Pressure-sensitive adhesive sheet and use thereof

ABSTRACT

A PSA sheet is provided, having an adhesive face formed of an acrylic PSA layer comprising an acrylic polymer. The PSA sheet has a peel strength of 5 N/10 mm or greater. The peel strength is measured as such that the adhesive face is directly adhered to an ethylene-propylene-diene rubber surface and after 20 minutes, peeled in the 180° direction at a tensile speed of 50 mm/min.

TECHNICAL FIELD

The present invention relates to a pressure-sensitive adhesive sheethaving an acrylic PSA. This invention also relates to apressure-sensitive adhesive sheet-bearing part that uses thepressure-sensitive adhesive sheet.

The present application claims priority to Japanese Patent ApplicationPublication Nos. 2013-144048, 2013-144049 and 2013-144050 filed on Jul.9, 2013; and the entire contents thereof are incorporated herein byreference.

BACKGROUND ART

In general, pressure-sensitive adhesive (PSA) has properties to be in asoft solid (viscoelastic) state in a room temperature range and easilyadhere to adherend with some pressure applied. In particular, acrylicPSA is superior in lightfastness, weatherability, oil resistance, etc.,to rubber-based PSA; and therefore, PSA sheets having acrylic PSA arewidely used for joining, fastening and so on in various fields.Technical literatures related to PSA sheet using acrylic PSA includePatent Documents 1 to 3.

CITATION LIST Patent Literature [Patent Document 1] Japanese PatentApplication Publication No. 2011-111594 [Patent Document 2] JapanesePatent Application Publication No. 2011-84732 [Patent Document 3] WO2013/005507 SUMMARY OF INVENTION Technical Problem

An adhesive face (a surface adhered to adherend) formed with acrylic PSAtends to be less adhesive (typically evaluated by its peel strength) toa low-polar adherend such as polyethylene, polypropylene, ethylenepropylene diene rubber (EPDM), etc., than to a high-polar adherend.Especially, olefinic rubber materials such as EPDM and thermoplasticolefinic elastomer (TPO) have low polarity and also comprise, ingeneral, a great deal of plasticizer such as paraffin oil; andtherefore, they are known as poorly adhesive materials with respect toacrylic PSA. It will be beneficial if the adhesiveness of a PSA sheethaving acrylic PSA to these low-polar materials and poorly adhesivematerials can be increased.

An objective of the present invention is to provide a PSA sheet that hasan acrylic PSA and exhibits great adhesion to various types of adherendincluding a low-polar adherend.

Another objective of the present invention is to provide a PSA sheetthat has an acrylic PSA and exhibits improved adhesion to an olefinicrubber material. Another related objective is to provide a PSAsheet-bearing part in which a PSA sheet having an acrylic PSA is adheredto a surface of an olefinic rubber material and a method for producingthe same.

As described above, an adhesive face formed of acrylic PSA tends to showinsufficient adhesion to olefinic rubber materials. Thus, olefinicrubber materials are often provided with primer layers and acrylic PSAis applied via the primer layers to the olefinic rubber materials. Asfor the primer layer-forming material, a material (e.g. chlorinatedpolypropylene) adhesive to both olefinic rubber materials and acrylicPSA is used.

However, a typical conventional primer layer is formed by applying asolution (primer solution) that comprises primer layer-formingcomponents in an organic solvent and allowing it to dry. If formation ofsuch a primer layer can be omitted, it will be preferable from thestandpoint of lowering environmental stress and reducing costs relatedto the primer layer formation (e.g. reducing material costs, energycosts, facility costs, etc.) and so on.

Accordingly, another objective of this invention is to provide a PSAsheet that comprises an adhesive face formed of an acrylic PSA, yetexhibits excellent adhesion even when applied to a surface of anolefinic rubber material without the presence of a primer layer inbetween. Another related objective is to provide a PSA sheet-bearingpart in which an adhesive face formed of an acrylic PSA is joineddirectly and firmly to a surface of an olefinic rubber material.

Solution to Problem

To solve at least one of the problems described above, the following artis provided.

A PSA sheet provided by this description has an adhesive face formed ofan acrylic PSA layer. The PSA sheet is characterized by exhibiting apeel strength of 5 N/10 mm or greater. The peel strength is measured assuch that the adhesive face is directly adhered to a EPDM surface andafter 20 minutes, peeled in the 180° direction at a tensile speed of 50mm/min. This peel strength may be referred to as the “to-EPDM initialpeel strength” hereinafter.

Such a PSA sheet that shows high initial peel strength when directlyapplied to a EPDM surface (e.g. without the presence of a primer layerin-between) is useful since it may provide excellent adhesion to EPDMand other olefinic rubber materials.

In a preferable embodiment of the PSA sheet disclosed herein, the PSAsheet comprises a support layer comprising a bubble-containing layer andan acrylic PSA layer supported with the support layer. According to suchan embodiment, a higher-performance PSA sheet can be obtained due to thenature of the acrylic PSA layer forming the adhesive face combined withthe nature of the support layer supporting the acrylic PSA layer.

A preferable example of the bubble-containing layer in the art disclosedherein is a bubble-containing adhesive layer formed of a PSA includingbubbles. Another preferable example of the bubble-containing layer is afoam sheet comprising a foam layer (typically a non-adhesive layer)formed of a plastic foam body. The PSA sheet disclosed herein may have aconfiguration including either a bubble-containing adhesive layer or afoam sheet or a configuration including both.

The PSA sheet disclosed herein preferably has a 10% compression hardnessin a range of 0.01 Pa to 0.07 Pa. Such a PSA sheet may be balanced wellin handling properties and conformability to a surface structure anddeformation of adherend. Thus, for instance, when the adherend is formedwith EPDM or other olefinic rubber material, the PSA sheet may haveexcellent properties to conform elastic deformation of such adherend tomaintain tight contact with its surface.

The PSA sheet disclosed herein preferably has a breaking strength in arange of 0.3 Pa to 2.5 Pa. Such a PSA sheet may be balanced well incohesion and conformability to a surface structure and deformation ofadherend. Thus, for instance, when the adherend is formed with EPDM orother olefinic rubber material, the PSA sheet may be suitable for fixingthe adherend to a desirable location while resisting repulsion of suchadherend.

The PSA sheet disclosed herein preferably has an overall thickness in arange of 0.05 mm to 10 mm Such a PSA sheet is preferable since adhesionto EPDM and other olefinic rubber materials can be easily balanced withcohesion.

The PSA sheet provided by this description can produce great adhesioneven in an embodiment of use where it is directly applied to EPDM orother olefinic rubber material surface. According to such an embodimentof use, a step of forming a primer layer can be omitted. Accordingly,the PSA sheet disclosed herein is preferable as the PSA sheet for directapplication to an olefinic rubber surface. The PSA sheet provided bythis description can be preferably used also in an embodiment where itis applied via a primer layer to an olefinic rubber material surface.

This description provides a PSA sheet-bearing part. The PSAsheet-bearing part comprises a part having a surface formed of anolefinic rubber material (or an olefinic rubber surface, hereinafter)and a PSA sheet of which at least one surface is formed as an adhesiveface. The adhesive face can be a surface of an acrylic PSA layercomprising an acrylic polymer. The PSA sheet is directly adhered at itsadhesive face to the olefinic rubber surface of the part. The PSA sheethas a peel strength of 7 N/10 mm or greater when it is peeled from theolefinic rubber surface in the 180° direction at a tensile speed of 50mm/min.

Such a PSA sheet-bearing part in which the PSA sheet is joined directlyand firmly to the olefinic rubber surface is preferable for anapplication where, for instance, the part is attached via the PSA sheetto a desirable location (possibly a surface of another part). In the PSAsheet-bearing part, the adhesive face of the PSA sheet is directlyadhered to the olefinic rubber surface. That is, in the PSAsheet-bearing part, no primer layer is present between the adhesive faceand olefinic rubber surface. The PSA sheet-bearing part in such aconfiguration is preferable from the standpoint of reducingenvironmental stress and costs. Because the adhesive face is formed asthe surface of the acrylic PSA layer, it is also preferable from thestandpoint of the weatherability and lightfastness.

From the standpoint of the conformability to a surface structure anddeformation of the part and the handling properties of the PSA sheet,etc., the PSA sheet constituting the PSA sheet-bearing part disclosedherein preferably has a 10% compression hardness of 0.01 Pa to 0.07 Pa.

From the standpoint of achieving cohesion and conformability to asurface structure and deformation of the part in a well-balanced manner,the PSA sheet constituting the PSA sheet-bearing part disclosed hereinpreferably has a breaking strength in a range of 0.3 Pa to 2.5 Pa.

From the standpoint of achieving cohesion and adhesion to the part, thePSA sheet constituting the PSA sheet-bearing part preferably has anoverall thickness in a range of 0.05 mm to 10 mm.

In a preferable embodiment of the PSA sheet-bearing part disclosedherein, the part is a weather strip. According to such a PSAsheet-bearing part (i.e. a PSA sheet-bearing weather strip), because ofthe high adhesion of the PSA sheet to the weather strip, the weatherstrip can be properly joined via the PSA sheet to a suitable location.

To solve at least one of the problems described above, the following artis further provided.

Another PSA sheet provided by this description has at least one surfaceformed as an adhesive face. The at least one surface is a surface of anacrylic PSA layer comprising an acrylic polymer. The acrylic polymercomprises an amino group-containing (meth)acrylate as its monomericcomponent. The PSA sheet includes at least one bubble-containing layer.In the PSA sheet in such a configuration, the adhesive face may exhibitgreat adhesion to a low-polar adherend because of the effects of theamino group-containing (meth)acrylate. As a result, great adhesion canbe achieved relative to various types of adherend including a low-polaradherend. With the inclusion of the bubble-containing layer, the PSAsheet shows great conformability to a surface structure and deformationof an adherend and the adhesive face is likely to maintain tight contactwith the adherend surface. Combined with the effects of the use of theamino group-containing (meth)acrylate, this may advantageouslycontribute to increase the adhesion to various types of adherendincluding a low-polar adherend.

In a preferable embodiment of the PSA sheet disclosed herein, the PSAsheet comprises a support layer including the bubble-containing layer aswell as the acrylic PSA layer supported with the support layer.According to such an embodiment, a higher-performance PSA sheet can beobtained due to the nature of the acrylic PSA layer forming the adhesiveface combined with the nature of the support layer supporting theacrylic PSA layer.

A preferable example of the bubble-containing layer in the art disclosedherein is a bubble-containing adhesive layer formed from a PSAcomprising bubbles. Another preferable example of the bubble-containinglayer is a foam sheet comprising a foam layer (typically a non-adhesivelayer) formed with a plastic foam body. The PSA sheet disclosed hereinmay have a configuration including either a bubble-containing adhesivelayer or a foam sheet or a configuration including both.

Preferably, the PSA sheet disclosed herein comprises thebubble-containing layer and a 10% compression hardness in a range of0.01 Pa to 0.07 Pa. Such a PSA sheet may be balanced well in handlingproperties and conformability to a surface structure and deformation ofadherend.

Preferably, the PSA sheet disclosed herein comprises thebubble-containing layer and a breaking strength in a range of 0.3 Pa to2.5 Pa. Such a PSA sheet may be balanced well in cohesion andconformability to a surface structure and deformation of adherend.

To solve at least one problem described above, the following art isfurther provided.

In particular, another PSA sheet provided by this description has anadhesive face to be applied to a surface formed of an olefinic rubbermaterial (or an olefinic rubber surface hereinafter). The adhesive faceis a surface of an acrylic PSA layer comprising an acrylic polymer. Theacrylic polymer comprises an amino group-containing (meth)acrylate asits monomeric component. The PSA sheet in such a configuration mayexhibit excellent adhesion to an olefinic rubber surface (e.g. a surfaceformed of EPDM) due to the effects of the amino group-containing(meth)acrylate.

The amino group-containing (meth)acrylate is preferably included at aratio higher than 2.6% by mass of the monomeric components of allpolymers (or “all monomeric components” hereinafter) in the acrylic PSAlayer. The PSA sheet having such an acrylic PSA layer may show greateradhesion to an olefinic rubber surface.

The acrylic PSA layer may be a layer formed with an acrylic PSAcomposition. In a preferable embodiment, the acrylic PSA compositioncomprises a polymerization product (a) of a monomer mixture comprisingan acyclic alkyl (meth)acrylate. The monomer mixture preferablycomprises the amino group-containing (meth)acrylate. Its ratio ispreferably above 0.2% by mass of the monomer mixture. The PSA sheethaving such an acrylic PSA layer may show greater adhesion to anolefinic rubber surface.

The art disclosed herein can be preferably practiced in an embodimentwhere the acrylic PSA layer is a layer formed with an acrylic PSAcomposition, with the acrylic PSA composition comprising apolymerization product (a) of a monomer mixture that comprises anacyclic alkyl (meth)acrylate and further comprising an acrylic oligomer(b) having a weight average molecular weight (Mw) of 2×10⁴ or lower.Herein, it is preferable that at least either the polymerization product(a) or the acrylic oligomer (b) comprises the amino group-containing(meth)acrylate as its monomeric component. The PSA sheet having such anacrylic PSA layer may exhibit grater adhesion to an olefinic rubbersurface. In a preferable embodiment, each of the polymerization product(a) and the acrylic oligomer (b) comprises the amino group-containing(meth)acrylate as its monomeric component. In such an embodiment, thePSA sheet can be brought about with yet greater adhesion to an olefinicrubber surface.

As described earlier, conventional general acrylic PSA tends to showinsufficient adhesion to olefinic rubber materials. Thus, primer layersare often provided to surfaces of olefinic rubber materials and acrylicPSA is adhered via the primer layers to the olefinic rubber materials.As for the primer layer-forming material, a material (e.g. chlorinatedpolypropylene) adhesive to both olefinic rubber materials and acrylicPSA is used.

The PSA sheet provided by this description for application to olefinicrubber can exhibit great adhesion also in an embodiment of use where thePSA sheet is directly applied to an olefinic rubber surface without thepresence of a primer layer in-between. According to such an embodimentof use, a step of forming a primer layer on the olefinic rubber materialsurface can be omitted. Thus, the PSA sheet disclosed herein forapplication to olefinic rubber is suitable as a PSA sheet that isdirectly applied to an olefinic rubber surface. The PSA sheet providedby this description for application to olefinic rubbers can also bepreferably used in an embodiment where it is applied via a primer layerto an olefinic rubber material surface.

This description also provides a PSA sheet-bearing part. The PSAsheet-bearing part comprises a part having an olefinic rubber surface (asurface formed of an olefinic rubber material) and a PSA sheet in whichat least one surface is formed as an adhesive face. The PSA sheet isadhered at the adhesive face to the olefinic rubber surface of the part.The adhesive face may be a surface of an acrylic PSA layer comprising anacrylic polymer. The acrylic polymer comprises an amino group-containing(meth)acrylate as its monomeric component. With respect to the PSAsheet-bearing part in such a configuration, the adhesive face of the PSAsheet shows great adhesion to an olefinic rubber surface; and therefore,the PSA sheet can be firmly adhered to the part. Accordingly, the PSAsheet is preferable for an application where the olefinic rubbersurface-bearing part is fastened via the PSA sheet to a desirablelocation (possibly a surface of another part).

In a preferable embodiment of the PSA sheet-bearing part disclosedherein, the adhesive face of the PSA sheet is directly adhered to thesurface formed of the olefinic rubber (i.e. without the presence of alayer such as a primer layer between the adhesive face and the olefinicrubber surface). In the PSA sheet-bearing part, because of the effectsof the amino group-containing (meth)acrylate, the adhesive face exhibitsgreat adhesion to an olefinic rubber surface and thus the part can bepreferably made in such an embodiment.

In a preferable embodiment of the PSA sheet-bearing part disclosedherein, the primary component of the polymer in the olefinic rubbermaterial is EPDM. According to such an embodiment, the effects of theinclusion of the PSA layer comprising an acrylic polymer having thecomposition disclosed herein can be produced particularly well.

The PSA sheet disclosed herein for application to olefinic rubber can bepreferably used in an embodiment where it is applied to a surface of anolefinic rubber material whose primary polymer component is EPDM.According to such an embodiment, the effects of the inclusion of a PSAlayer comprising an acrylic polymer having the composition disclosedherein can be produced particularly well.

The olefinic rubber material comprises carbon black in a preferableembodiment of the PSA sheet-bearing part or PSA sheet for application toolefinic rubber disclosed herein. In an embodiment of use where it isapplied to a surface of an olefinic rubber material comprising carbonblack, the effects of the inclusion of a PSA layer comprising an acrylicpolymer having the composition disclosed herein can be producedparticularly well.

In a preferable embodiment of the PSA sheet-bearing part disclosedherein, the part having the surface formed of the olefinic rubbermaterial is a weather strip. According to such a PSA sheet-bearing part(i.e. a PSA sheet-bearing weather strip), because of the high adhesionof the PSA sheet to the weather strip, the weather strip can be properlyattached via the PSA sheet to a suitable location.

This description also provides a method for producing a PSAsheet-bearing part. The method comprises a step of obtaining a moldedolefinic rubber body having an olefinic rubber surface (a surface formedof an olefinic rubber material). It also includes a step of obtaining aPSA sheet in which at least one surface is formed as an adhesive face.The method comprises a step of applying the adhesive face to theolefinic rubber surface. Preferably, the step of applying the adhesiveface can be a step of applying the adhesive face directly (i.e. withoutthe presence of another layer) to the olefinic rubber surface. Herein,the adhesive face is a surface of an acrylic PSA layer comprising anacrylic polymer. The acrylic polymer comprises an amino group-containing(meth)acrylate as its monomeric component. According to such a method,by the effects of the amino group-containing (meth)acrylate, a PSAsheet-bearing part in which a PSA sheet is firmly adhered to a surfaceof a molded olefinic rubber body can be produced.

The PSA sheet-bearing part production method disclosed herein can bepreferably practiced in an embodiment where the surface formed of theolefinic rubber material is subjected to cleaning treatment by which acleaning liquid comprising an organic solvent is allowed to make contactwith the surface and the adhesive face is directly applied to thecleaned surface. According to such an embodiment, the PSA sheet-bearingpart can be produced with the PSA sheet being more firmly joined to thesurface of the molded olefinic rubber body.

In a preferable embodiment, the step of applying the adhesive face tothe olefinic rubber surface can be carried out at ordinary temperature.Such an embodiment is preferable because it can save energy costs ascompared to an embodiment where, for instance, one or each of the moldedolefinic rubber body or the PSA sheet is heated when the molded body isapplied to the PSA sheet. It is also preferable in view that theapplication can be done with simpler equipment.

The PSA sheet-bearing part production method disclosed herein can bepreferably practiced in an embodiment where the molded olefinic rubberbody is a weather strip. According to a PSA sheet-bearing weather stripproduced in such an embodiment, the weather strip can be properlyattached via the PSA sheet to a desirable location.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a schematic cross-sectional view of the configuration ofthe PSA sheet according to an embodiment.

FIG. 2 shows a schematic cross-sectional view of the configuration ofthe PSA sheet according to another embodiment.

FIG. 3 shows a schematic cross-sectional view of the configuration ofthe PSA sheet according to another embodiment.

FIG. 4 shows a schematic cross-sectional view of the configuration ofthe PSA sheet according to another embodiment.

FIG. 5 shows a schematic cross-sectional view of the configuration ofthe PSA sheet according to another embodiment.

FIG. 6 shows a schematic cross-sectional view of the configuration ofthe PSA sheet according to another embodiment.

FIG. 7 shows a schematic cross-sectional view of the configuration ofthe PSA sheet according to another embodiment.

FIG. 8 shows a schematic cross-sectional view of a PSA sheet-bearingpart (an article having the PSA sheet) according to an embodiment.

FIG. 9 shows a schematic cross-sectional view of a PSA sheet-bearingpart (an article having the PSA sheet) according to another embodiment.

FIG. 10 shows a flow chart illustrating the PSA sheet-bearing partproduction method according to an embodiment.

DESCRIPTION OF EMBODIMENTS

Preferred embodiments of the present invention are described below.Matters necessary to practice this invention other than thosespecifically referred to in this description can be understood by aperson skilled in the art based on the disclosure about implementing theinvention in this description and conventional techniques in thepertinent field. The present invention can be practiced based on thecontents disclosed in this description and conventional techniques inthe subject field.

In the drawings referenced below, a common reference numeral may beassigned to members or sites producing the same effects, and duplicateddescriptions are sometimes omitted or simplified. The embodimentsdescribed in the drawings are schematized for clear illustration of thepresent invention, and do not necessarily represent the accurate size orreduction scale of the PSA sheet of this invention actually provided asa product.

As described earlier, the term “PSA” in this description refers to amaterial present in a soft solid (viscoelastic) state in a roomtemperature range and has a property to easily adhere to adherend withsome pressure applied. As defined in “Adhesion Fundamental and Practice”by C. A. Dahlquist (McLaren & Sons (1966), P. 143), the PSA referred toherein is a material having a property that satisfies complex tensilemodulus E*(1 Hz)<10⁷ dyne/cm² (typically, a material exhibiting thedescribed characteristics at 25° C.).

As used herein, the term “(meth)acryloyl” comprehensively refers toacryloyl and methacryloyl. Similarly, the term “(meth)acrylate”comprehensively refers to acrylate and methacrylate, and the term“(meth)acryl” comprehensively refers to acryl and methacryl. The term“(cyclo)alkyl” comprehensively refers to acyclic alkyl and cycloalkyl.The “(cyclo)alkyl” is sometimes referred to simply as the “alkyl.”

In this description, the term “acrylic monomer” refers to a monomerhaving at least one (meth)acryloyl group per molecule. The term “acrylicpolymer” refers to a polymer that comprises an acrylic monomer as amonomer unit (monomeric component) constituting the polymer. In otherwords, it refers to a polymer comprising a monomer unit derived from anacrylic monomer. Thus, the “acrylic polymer” referred to herein maycomprise, as a part or the entirety of its monomeric components, anacrylic monomer having at least one methacryloyl group per molecule.

The term “primary component” in this description typically refers to acomponent accounting for more than 50% by mass of the content, unlessotherwise specified. For instance, an alkyl (meth)acrylate being theprimary component of a monomer mixture typically means that more than50% by mass of the monomer mixture is the alkyl (meth)acrylate. Forinstance, EPDM being the primary component of a polymer in an olefinicrubber material typically means that more than 50% by mass of the totalamount of the polymer in the olefinic rubber material is EPDM.

In the description below, the term “standard EPDM piece” refers to thestandard EPDM test piece specified in Section 3.1.4, WorldwideEngineering Standards, Material Specification Adhesives, GMW 15201(published December, 2010) by General Motors. That is, it refers to a33.4 mm wide by 3.2 mm thick rectangular EPDM piece, ASTM D2000-00,Shore A, 70 durometer (black) dense (EPDM), available from LaurenManufacturing, or to an equivalent product.

In this description, the term “active energy ray” refers to an energyray having energy enough to cause a chemical reaction, such aspolymerization reaction, crosslinking reaction, initiator decomposition,etc. Examples of the active energy rays referred to herein include lightsuch as UV rays, visible light, infrared rays, etc., as well asradiation such as α-rays, δ-rays, γ-rays, electron beam, neutron beam, Xrays, etc.

As used herein, the term “PSA layer” herein refers to a layer having apeel strength of 0.1 N/20 mm or greater when measured based on JIS20237(2004), where, with a SUS304 stainless steel plate being anadherend, it is press-bonded to the adherend with a 2 kg roller movedback and forth once in a measurement environment at 23° C. and after 30minutes, it is peeled in the 180° direction at a tensile speed of 300mm/min.

As used herein, the term “non-adhesive layer” refers to a layer that isnot considered as a PSA layer, typically referring to a layer having apeel strength of less than 0.1 N/20 mm. A layer that does not stick to aSUS304 stainless steel plate when press-bonded to the stainless steelplate with a 2 kg roller moved back and forth once (i.e. a layer that isessentially non-adhesive on the stainless steel plate) in an measurementenvironment at 23° C. is a typical example included in the concept ofthe non-adhesive layer referred to herein.

In this description, the term “bubble-containing layer” refers to alayer wherein, at 25° C., the ratio of volume of bubbles in the apparentvolume of the layer is 3% or higher by volume (typically 5% or higher byvolume).

In this description, the term “bubble-free layer” refers to a layer thatis not considered as a bubble-containing layer. In particular, it refersto a layer in which the ratio of volume of bubbles in the apparentvolume of the layer is lower than 3% by volume (typically lower than 1%by volume).

In this description, the term “plastic film” typically refers tonon-porous plastic film and is conceptually distinct from woven andnonwoven fabrics formed of plastic fibers or from a foam sheet. Theplastic film in this description typically belongs to the bubble-freelayer.

<Adhesion to Standard EPDM Plate>

The PSA sheet disclosed herein has an adhesive face formed with anacrylic PSA layer comprising an acrylic polymer. The PSA sheetpreferably has, but not particularly limited to, a to-EPDM initial peelstrength of 5 N/10 mm or greater.

Herein, the “to-EPDM initial peel strength” refers to the value measuredby the following method, using the standard EPDM piece described aboveor an equivalent product as the adherend.

[Measurement Method of to-EPDM Initial Peel Strength]

A PSA sheet to be measured is prepared into a 10 mm wide strip to make ameasurement sample. When the PSA sheet to be measured is in a form ofdouble-faced PSA sheet, 50 μm thick polyethylene terephthalate (PET)film should be applied to back one of the adhesive faces in advance.

The standard EPDM plate surface as the adherend is cleaned by wipingtwice in one direction with cloth wet with isopropanol (IPA) (cleaningtreatment).

In a standard environment at 23° C. and 50% RH, to the cleaned adherendsurface, the adhesive face of the measurement sample is press-bondedwith a roller weighing about 2 to 5 kg moved back and forth once. Afterthe resultant is stored in the standard environment for 20 minutes, 180°peel strength (N/10 mm) is measured in the same environment, based onJIS Z0237(2004). The measurement is taken twice and their arithmeticaverage value is used as the to-EPDM initial peel strength (N/10 mm).

The 180° peel strength can be measured, using a commercial generaltensile tester. For instance, a universal tensile and compressiontesting machine (available from Minebea Co., Ltd., system name“Tensile/Compression Tester, TG-1kN”) can be used.

When it is difficult to prepare a measurement sample in a 10 mm widestrip such as when the width of the PSA sheet is smaller than 10 mm, ameasurement sample measuring a mm in width is used; and the product ofthe measured value of peel strength (N/α mm) multiplied by 10/α is usedas the value instead.

In the PSA sheet disclosed herein, the adhesive face preferably has ato-EPDM initial peel strength of 5 N/10 mm or greater. The to-EPDMinitial peel strength is preferably 7 N/10 mm or greater, morepreferably 10 N/10 mm or greater, or yet more preferably 15 N/10 mm orgreater. The PSA sheet showing such to-EPDM initial peel strength canbring about excellent initial adhesion to EPDM and other olefinic rubbermaterials. Such a PSA sheet is preferable, for instance, as a componentof a PSA sheet-bearing part (e.g. a PSA sheet-bearing weather strip)described later.

The upper limit of the to-EPDM initial peel strength is not particularlylimited. It is usually 100 N/10 mm or less, or typically 50 N/10 mm orless.

The PSA sheet preferably has a peel strength of 7 N/10 mm or greaterwhen directly applied to the standard EPDM plate surface and after 7days, peeled in the 180° direction at a tensile speed of 50 mm/min.Herein, the peel strength after 7 days refers to the value measured inthe same manner as for the to-EPDM initial peel strength except that thestorage period in the standard environment at 23° C. and 50% RH from thepress-bonding of the adhesive face to the adherend is 7 days.Hereinafter, the peel strength after 7 days is sometimes referred to asthe “post-aging to-EPDM peel strength.”

A PSA sheet having a post-aging to-EPDM peel strength of 7 N/10 mm orgreater may exhibit excellent adhesion to EPDM and other olefinic rubbermaterials for a long time. Thus, such a PSA sheet is preferable, forinstance, as a component of a PSA sheet-bearing part (e.g. a PSAsheet-bearing weather strip) described later. Such a PSA sheet may bepreferable, for instance, in a form of double-faced PSA sheet for anapplication where a part having a surface formed of EPDM or otherolefinic rubber material is joined to a desirable location and likeapplication. From the standpoint of the reliability of the joint, etc.,the post-aging to-EPDM peel strength is preferably 10 N/10 mm orgreater, more preferably 15 N/10 mm or greater, or yet more preferably20 N/10 mm or greater.

The upper limit of the post-aging to-EPDM peel strength is notparticularly limited. It is usually 100 N/10 mm or less, or typically 50N/10 mm or less.

In a preferable embodiment of the PSA sheet provided by thisdescription, the PSA sheet satisfies each of the following:

(1) having a to-EPDM initial peel strength of 5 N/10 mm or greater(preferably 7 N/10 mm or greater, more preferably 10 N/10 mm or greater,or yet more preferably 15 N/10 mm or greater); and(2) having a post-aging to-EPDM peel strength of 7 N/10 mm or greater(preferably 10 N/10 mm or greater, more preferably 15 N/10 mm orgreater, or yet more preferably 20 N/10 mm or greater). Such a PSA sheetis preferable, for instance, as a component of a PSA sheet-bearing part(e.g. a PSA sheet-bearing weather strip).

<Configuration of PSA Sheet>

The shape and structure of the PSA sheet disclosed herein is notparticularly limited. For instance, the PSA sheet may have asingle-layer structure formed with one acrylic PSA layer or amulti-layer structure including an adhesive face-constituting acrylicPSA layer whose back face (opposite from the adhesive face) is laminatedwith a non-release surface of another layer. The other layer can be anacrylic PSA layer, a different PSA layer, or a non-adhesive layer.

The concept of PSA sheet referred to herein encompasses so-called PSAtape, PSA labels, PSA film and so on. The PSA layer is typically formedin a continuous manner, but it is not limited to such a form. Forinstance, it may be formed in a regular or random pattern of dots,stripes, etc. The PSA sheet provided by this invention may be in a rollform or in a flat sheet form. Alternatively, the PSA sheet may beprocessed into various shapes.

[Bubble-Containing Layer]

In a preferable embodiment of the PSA sheet disclosed herein, the PSAsheet comprises a bubble-containing layer. The bubble-containing layercan be thought as a layer that includes bubble structures. The “bubblestructures” should just be structures having a gaseous component. Theycan be “bubbles” that are formed of solely the gaseous component and arestructurally free of outer shells or they can be of a substance in aform of particles having hollow structures where the gaseous componentis enclosed in outer shells (or such a substance may be referred to as“hollow particles” hereinafter). The material constituting the outershells is not particularly limited. It can be an inorganic material suchas glass or an organic material.

The bubble-containing layer can be an acrylic PSA layer constituting thefirst surface (first adhesive face) of the PSA sheet. When the PSA sheetcomprises another layer in addition to the acrylic PSA layerconstituting the first adhesive face, this other layer can be abubble-containing layer. When the other layer is a bubble-containinglayer, the bubble-containing layer can be a layer that is adhesive atordinary temperature (i.e. a bubble-containing adhesive layer) or alayer that is essentially non-adhesive at ordinary temperature (i.e. abubble-containing non-adhesive layer). In the PSA sheet having amultiple layer-containing structure (multi-layer structure) thatincludes two or more layers, the number of bubble-containing layersamong the multiple layers can be one or can be two or more.

The inclusion of the bubble-containing layer in the PSA sheet providesadequate cushioning properties to the PSA sheet. By this, the adhesiveface can absorb unevenness and a gap in the adherend surface, wherebythe adhesive face can be adhered more tightly to the adherend surface.The tight adhesion of the adhesive face to the adherend surface mayadvantageously contribute to increase the adhesion to EPDM and otherolefinic rubber surfaces. The bubble-containing layer may contribute toincrease the flexibility (reduce the repulsive force) of the PSA sheet.By this, when the PSA sheet is applied along a curved surface or asurface having a gap or when the adherend to which the PSA sheet isadhered is deformed, etc., peeling (lifting) of the PSA sheet from thesurface caused by its own repulsive force can be effectively inhibited.

The bubble structures in the bubble-containing layer disclosed hereinmay be formed solely with gas bubbles (i.e. shell-free gas bubbles),solely with hollow particles, or with both gas bubbles and hollowparticles. From the standpoint of the cushioning properties, etc., apreferable PSA sheet has a bubble-containing layer that comprises atleast bubble structures formed with gas bubbles.

The bubbles contained in the bubble-containing layer may be independent(separate) bubbles, successive bubbles, or a mixture of these. From thecushioning properties, a more preferable bubble-containing layer isformed to include many independent bubbles. With respect to independentbubbles, the gaseous component included in the bubbles (gas componentforming the bubbles; or “bubble-forming gas” hereinafter) is notparticularly limited, and it can be various gaseous components such asinert gases including nitrogen, carbon dioxide, argon, etc., as well asvarious gaseous components such as air, etc. When the polymerization,etc., are carried out in a state containing the bubble-forming gas, itis preferable to use, as the bubble-forming gas, a gas species that doesnot inhibit the reaction(s). From such a standpoint and in respect ofthe cost, etc., nitrogen can be preferably used as the bubble-forminggas.

In typical, the shapes of bubbles are more or less globular while theyare not limited to such shapes. The average diameter of bubbles (averagebubble diameter) is not particularly limited. It can be selected, forinstance, from a range of 1 μm to 1000 μm, preferably 10 μm to 500 μm,or more preferably 30 μm to 300 μm. The average bubble diameter isusually suitably at most 50% of the thickness of the bubble-containinglayer, or preferably at most 30% (e.g. at most 10 V.

The average bubble diameter can be determined typically by scanningelectron microscopy (SEM), preferably by measuring 10 or more bubblesfor their diameters and arithmetically averaging the results. For this,with respect to non-globular bubbles, they are converted to globularbubbles having the same volumes to determine the average bubblediameter.

The volume ratio (bubble content) of bubbles in the bubble-containinglayer is not particularly limited. It can be suitably set so as toobtain target cushioning properties and flexibility. For instance, itcan be 5 to 50% by volume of the volume of the entire bubble-containinglayer (referring to the apparent volume which can be determined from thesurface area and thickness of the bubble-containing layer). When thebubble-containing layer is a PSA layer, in view of the balance betweenthe effects of the inclusion of bubbles and adhesive properties, thevolume ratio of bubbles is suitably, for instance, 8 to 40% by volume.

[Bubble-Containing Adhesive Layer]

The bubble-containing layer may be an acrylic PSA layer constituting anadhesive face. In a PSA comprising another layer in addition to theadhesive face-constituting acrylic PSA layer, the other layer can be abubble-containing layer. The other layer can be a bubble-containingadhesive layer constituting an adhesive face different from the adhesiveface formed with the acrylic PSA layer, or a bubble-containing adhesivelayer or bubble-containing non-adhesive layer that does not constitutean adhesive face. When the other layer is a bubble-containing adhesivelayer, the adhesive layer can be an acrylic PSA layer or a non-acrylicPSA layer. The non-acrylic PSA layer can be a rubber-based PSA layer,polyester-based PSA layer, urethane-based PSA layer, silicone-based PSAlayer, or the like.

In the PSA layer in an embodiment comprising a bubble-containingadhesive layer as the non-acrylic PSA layer constituting an adhesiveface, from the standpoint of the cushioning properties and flexibility,etc., the PSA constituting the bubble-containing adhesive layer has, butnot particularly limited to, a glass transition temperature (Tg) ofpreferably −40° C. or lower, or more preferably −50° C. or lower basedon the composition of all monomeric components of the PSA. The lowerlimit of the Tg is not particularly limited. It is typically −80° C. orhigher, for instance, −70° C. or higher.

In a preferable embodiment, as the PSA constituting thebubble-containing adhesive layer, it is preferable to use a PSA whose Tgbased on the composition of its all monomeric components is lower thanthe Tg based on the composition of all monomeric components of theadhesive face-constituting acrylic PSA layer. This can bring about ahigh performance PSA sheet that combines high adhesion to EPDMcontributed primarily by the acrylic PSA layer constituting the adhesiveface and great cushioning properties contributed primarily by thebubble-containing adhesive layer. For instance, relative to the Tg ofthe adhesive face-constituting acrylic PSA layer, the Tg of the PSAconstituting the bubble-containing adhesive layer is lower preferably by5° C. or more, more preferably aby 10° C. or more, or yet morepreferably by 15° C. or more (e.g. by 20° C. or more). In a PSA sheetcomprising an acrylic PSA layer as a bubble-containing adhesive layer,it is particularly meaningful to satisfy the relationship of their Tgvalues.

As the method for forming such a bubble-containing layer, for instance,the following methods can be suitably employed: (1) a method where a PSAcomposition having a pre-mixed bubble-forming gas (preferably a PSAcomposition that cures with active energy rays such as UV rays to formPSA) is allowed to cure to form a bubble-containing adhesive layer, (2)a method where a PSA composition comprising a foaming agent is used toform bubbles from the foaming agent and thereby to form abubble-containing adhesive layer, and like method. The foaming agentused is not particularly limited. A suitable one can be selected fromcommonly-known foaming agents. For instance, foaming agents such asthermally expandable microspheres and the like can be preferably used.

In forming a bubble-containing adhesive layer by the method (1), themethod for preparing the PSA composition having a pre-mixedbubble-forming gas is not particularly limited, and a knownbubble-mixing method can be used. An example of a device comprises astator made of a finely toothed disc with a central open hole and arotor which opposes the stator and is similarly made of a finely tootheddisc. The PSA composition (PSA composition precursor) prior to bubblemixing is introduced between the stator's tooth and rotor's tooth inthis device. With the rotor spinning at a high speed, a gaseouscomponent (bubble-forming gas) is introduced to form bubbles through theopen hole into the PSA composition precursor. By this, a PSA compositioncan be obtained, having finely dispersed bubbles mixed therein.

By applying such a PSA composition having a bubble-forming gas mixedtherein to a prescribed surface and allowing it to cure, abubble-containing adhesive layer can be formed. As the curing method,methods such as heating and irradiating active energy rays (e.g. UVrays) can be preferably employed. The bubble-containing adhesive layercan be preferably formed by subjecting the PSA composition having abubble-forming gas mixed therein to heating, irradiation of activeenergy rays, etc., and allowing it to cure in a state where bubbles arestably kept.

From the standpoint of the mixing compatibility of the bubble-forminggas with the PSA composition precursor or the stability of bubbles, asurfactant may be added to the PSA composition. Examples of such asurfactant include ionic surfactants, hydrocarbon-based surfactants,silicone-based surfactants, fluorine-based surfactants and the like.Among these, fluorine-based surfactants are preferable. In particular, afluorine-based surfactant having an oxyalkylene group (typically anoxyalkylene group having 2 to 3 carbon atoms) along with a fluorinatedhydrocarbon group is preferable. Fluorine-based surfactants can be usedsingly as one species or in combination of two or more species. Examplesof preferably usable commercial fluorine-based surfactants include tradename “SURFLON S-393” available from AGC Seimi Chemical Co., Ltd.

The amount of fluorine-based surfactant used is not particularlylimited. For instance, the amount (based on non-volatiles) offluorine-based surfactant used to 100 parts by mass of all monomericcomponents in the bubble-containing adhesive layer can be about 0.01 to3 parts by mass. From the standpoint of obtaining greater effects of theuse of fluorine-based surfactant (e.g. an effect to enhance the mixingor stability of bubbles), its amount is suitably 0.03 part by mass orgreater, or preferably 0.05 part by mass or greater. When thebubble-containing adhesive layer constitutes an adhesive face, from thestandpoint of the adhesive properties, the amount of surfactant issuitably 2 parts by mass or less, preferably 1.5 parts by mass or less,or more preferably 1 part by mass or less.

[Bubble-Containing Non-Adhesive Layer]

When the PSA sheet disclosed herein has a bubble-containing non-adhesivelayer as a bubble-containing layer, the bubble-containing non-adhesivelayer can be, for instance, a known foam sheet. The material of the foamsheet is not particularly limited. For instance, foam sheets comprisingfoam body layers formed of foam bodies of various plastic materials(plastic foam bodies) can be preferably used. The type of plasticmaterial (including a rubber material) forming the plastic foam body isnot particularly limited. For the plastic material, solely one speciesor a combination of two or more species can be used.

Specific examples of plastic foam bodies include polyolefinic foambodies such as polyethylene foam bodies, polypropylene foam bodies,etc.; polyester-based foam bodies such as polyethylene terephthalatefoam bodies, polyethylene naphthalate foam bodies, polybutyleneterephthalate foam bodies, etc.; polyvinyl chloride-based foam bodiessuch as polyvinyl chloride foam bodies, etc.; vinyl acetate-based resinfoam bodies; polyphenylene sulfide resin foam bodies; polyamide-basedfoam bodies such as polyamide (nylon) resin foam bodies, wholly aromaticpolyamide (aramid) resin foam bodies, etc.; polyimide-based resin foambodies; acrylic foam bodies such as acrylic resin foam bodies; polyetherether ketone (PEEK) foam bodies; polystyrene-based foam bodies such aspolystyrene foam bodies; polyurethane-based foam bodies such aspolyurethane resin foam bodies; and the lie. The plastic foam body canbe a rubber-based foam body such as a polychloroprene rubber foam body.For instance, a polyolefinic foam sheet formed of a polyolefinic foambody, a polyester-based foam sheet formed of a polyester-based foambody, a polyimide-based foam sheet formed of a polyimide-based resinfoam body, an acrylic foam sheet formed from an acrylic foam body, apolystyrene-based foam sheet formed of a polystyrene-based foam body, apolyurethane-based foam sheet formed of a polyurethane-based foam body,a rubber-based foam sheet formed of a rubber-based foam body or the likecan be preferably used.

From the cushioning properties, a preferable foam sheet is formed of afoam body (elastic foam body) that exhibits adequate elasticity atordinary temperature. For instance, it is preferable to use a foam sheethaving a 10% compression hardness generally in a range of 0.007 Pa to0.07 Pa (more preferably 0.01 Pa to 0.07 Pa) when the 10% compressionhardness is measured in the same manner as for the 10% compressionhardness of PSA sheets described later. A PSA sheet comprising such afoam sheet as the bubble-containing layer is preferable because the 10%compression hardness of the PSA sheet can be readily adjusted to be in apreferable range described later.

An example of preferable foam bodies is a polyolefinic foam body. As forthe plastic material (i.e. a polyolefinic resin) forming thepolyolefinic foam body, various commonly known or used polyolefinicresins can be used without particular limitations. Examples includepolyethylenes such as a low-density polyethylene (LDPE), linearlow-density polyethylene (LLDPE), high-density polyethylene (HDPE),metallocene catalyst-based linear low-density polyethylene, etc.;polypropylenes; ethylene-propylene copolymers; ethylene-vinyl acetatecopolymers; and the like. These polyolefinic resins can be used singlyas one species or in a combination of two or more species.

From the standpoint of the weatherability, etc., preferable examples ofthe foam sheet include a polyethylene-based foam sheet essentiallyformed of a polyethylene-based resin foam body, a polypropylene-basedfoam sheet essentially formed of a polypropylene-based resin foam body,and the like. Herein, the polyethylene-based resin refers to a resinformed from ethylene as its primary monomer (the primary component amongmonomers, i.e. a component accounting for more than 50% by mass) and mayinclude HDPE, LDPE and LLDPE as well as ethylene-propylene copolymer andethylene-vinyl acetate copolymer in which the copolymerization ratio ofethylene exceeds 50% by mass. Similarly, the polypropylene-based resinrefers to a resin formed from propylene as its primary monomer. As forthe foam sheet in the art disclosed herein, a polyethylene-based foamsheet can be preferably used.

[Bubble-Free Layer]

When the PSA sheet disclosed herein comprises at least onebubble-containing layer and at least one bubble-free layer, thebubble-free layer can be an adhesive layer (bubble-free adhesive layer)or a non-adhesive layer (bubble-free non-adhesive layer).

When the bubble-free layer is an adhesive layer, the adhesive layer canbe an acrylic PSA layer or a non-acrylic PSA layer. The non-acrylic PSAlayer can be a rubber-based PSA layer, polyester-based PSA layer,urethane-based PSA layer, silicone-based PSA layer, or the like.

When the bubble-free layer is a non-adhesive layer, as the non-adhesivelayer, a suitable one can be selected and used in accordance of theapplication of the PSA sheet, such as plastic film includingpolypropylene film, ethylene-propylene copolymer film, polyester film,polyvinyl chloride film, etc.; metal foil such as aluminum foil, copperfoil, etc.; or the like. As the plastic film, either non-stretched filmor stretched (uni-axially stretched or bi-axially stretched) film can beused.

The PSA sheet disclosed herein may include a layer of woven fabric ornon-woven fabric (meaning to include paper such as Japanese paper(Washi), high-grade paper, etc.) of a single species or a blend, etc.,of various species of fibrous substance. The fibrous substance can benatural fibers such as hemp, cotton, etc.; synthetic fibers such aspolyester, vinylon, etc.; semi-synthetic fibers such as acetate; or thelike.

In this description, with respect to such a layer of a fibroussubstance, if spaces among fibers constituting the layer are filled withsome other material (PSA, thermoplastic resin, etc.), such a layer of afibrous substance is treated as a composite material layer including theother material and the fibrous substance. Thus, with the apparent volumeof the composite material layer being 100% by volume, when more than 97%by volume of the spaces among fibers of the fibrous substance are filledwith the other material, the composite material layer is treated as abubble-free layer. When 3% by volume or more of the inter-fiber spacesremains as bubbles, the composite material layer is treated as abubble-containing layer.

On the other hand, when the inter-fiber spaces are not filled with theother material in the fibrous substance layer, if the volume of bubblesaccounts for 3% by volume or more of the apparent volume of the fibroussubstance layer itself, this layer is treated as a bubble-containinglayer; and if it accounts for less than 3% by volume, it is treated as abubble-free layer.

The PSA sheet disclosed herein can be preferably made in an embodimentfree of such a fibrous substance layer.

FIG. 1 to FIG. 7 illustrate typical configurational examples of the PSAsheet disclosed herein.

Configurational Example 1

PSA sheet 1 shown in FIG. 1 is an adhesively double-faced PSA sheetformed of an acrylic PSA layer (first adhesive layer) 21 comprising anacrylic polymer. The PSA sheet 1 preferably has, but not particularlylimited to, a 20-min peel strength (to-EPDM initial peel strength) of 5N/10 mm or greater when measured upon direct application of either thefirst surface (first adhesive face) 21A or the second surface (secondadhesive face) 21B of the PSA layer 21 onto an EPDM surface.

Although not particularly limited to this, PSA sheet 1 in such aconfiguration can be preferably used in an embodiment where each of theadhesive faces 21A and 21B is applied to an olefinic rubber surface suchas EPDM. It can be preferably used also in an embodiment where the firstadhesive face 21A is applied to an olefinic rubber surface and thesecond adhesive face 21B is applied to various types of adherend surface(not limited to an olefinic rubber surface) and in like embodiment. ThePSA layer 21 may be a PSA layer having a multi-layer structure (laminatestructure) in which two or more multiple acrylic PSA layers arelaminated.

Configurational Example 2

PSA sheet 2 shown in FIG. 2 is a double-faced PSA sheet comprising afirst PSA layer 21 constituting the first adhesive face 21A, a secondPSA layer 22 constituting the second adhesive face 22A and anintermediate layer 23 placed between them. Among them, the first PSAlayer 21 is an acrylic PSA layer. In other words, the first adhesiveface 21A is a surface of an acrylic PSA layer (first PSA layer) 21. Thesecond PSA layer 22 can be an acrylic PSA layer or a non-acrylic PSAlayer. The non-acrylic PSA layer include a rubber-based PSA layer,polyester-based PSA layer, urethane-based PSA layer, silicone-based PSAlayer, etc. In the intermediate layer 23, its first surface 23A andsecond surface 23B are both non-releasable surfaces. The intermediatelayer 23 can be an adhesive layer or a non-adhesive layer. The PSA sheet2 preferably has, but not particularly limited to, a to-EPDM initialpeel strength of 5 N/10 mm or greater when measured at least withrespect to the first adhesive face 21A.

Although not particularly limited to this, PSA sheet 2 in such aconfiguration can be preferably used, for instance, in an embodimentwhere the first adhesive face 21A is applied to an olefinic rubbersurface such as EPDM and the second adhesive face 22A is applied tovarious types of adherend surface (not limited to an olefinic rubbersurface), etc.

When the intermediate layer 23 is an adhesive layer, the adhesive layercan be an acrylic PSA layer or a non-acrylic PSA layer. The non-acrylicPSA layer can be a rubber-based PSA layer, polyester-based PSA layer,urethane-based PSA layer, silicone-based PSA layer, etc.

When the intermediate layer 23 is a non-adhesive layer, as theintermediate layer 23, a suitable species can be selected and used inaccordance with the purpose of the PSA sheet, among, for instance,plastic films such as polypropylene films, ethylene-propylene copolymerfilms, polyester films, polyvinyl chloride films, etc.; foam sheets madeof foam such as polyurethane foam, polyethylene foam, polychloroprenefoam, etc.; woven fabrics and non-woven fabrics (meaning to includepaper such as Japanese paper (Washi), high-grade paper, etc.) of asingle species or a blend, etc., of various species of fibrous substance(which can be natural fibers such as hemp, cotton, etc.; syntheticfibers such as polyester, vinylon, etc.; semi-synthetic fibers such asacetate, etc.; and the like); metal foil such as aluminum foil, copperfoil, etc.; and the like. For the plastic film, either non-stretchedfilm or a stretched (uni-axially stretched or biaxially stretched) filmcan be used. One or each of the surfaces 23A and 23B of the intermediatelayer 23 can be subjected to a surface treatment to increase thenon-releasability of the surface(s), such as corona discharge treatment,primer layer formation, etc.

The PSA sheet 2 shown in FIG. 2 can be made also in an embodimentconsisting of the first PSA layer (acrylic PSA layer) 21 and theintermediate layer 23, with the intermediate layer 23 being an adhesivelayer. That is, it may have the same configuration as the one shown inFIG. 2, but without the second PSA layer 22. In the PSA sheet in thisembodiment, the second surface 23B of the intermediate layer 23 shown inFIG. 2 constitutes the second adhesive face. A sheet in such aconfiguration can be preferably used, for instance, in an embodimentwhere the first adhesive face 21A is applied to EPDM or other olefinicrubber surface and the other surface 23B of the intermediate layer 23 isapplied to various types of adherend surface (not limited to an olefinicrubber surface).

Configurational Example 3

PSA sheet 3 shown in FIG. 3 is an adhesively single-faced PSA sheetcomprising a first PSA layer 21 constituting the first surface (firstadhesive face) 21A and a backside layer 31 constituting the secondsurface 31A of the PSA sheet 3. The first PSA layer 21 is an acrylic PSAlayer. The backside layer 31 is a non-adhesive layer and at least itsfirst PSA layer 21—side surface 31B is not releasable. The backsidelayer 31 can be of, for instance, a plastic film, woven fabric,non-woven fabric, foam sheet, metal foil and the like exemplified as thenon-adhesive intermediate layer 23 in the description of FIG. 2. Whilenot particularly limited, the PSA sheet 3 preferably has a to-EPDMinitial peel strength of 5 N/10 mm or greater when measured with respectto the first adhesive face 21A.

PSA sheet (single-faced PSA sheet) 3 in such a configuration can bepreferably used, for instance, in an embodiment where the first adhesiveface 21A is applied to EPDM and other olefinic rubber surface. The firstPSA layer 21—side surface 31B of the backside layer 31 may be subjectedto a surface treatment to increase the non-releasing properties of thesurface, such as corona discharge treatment, primer layer formation,etc. Of the backside layer 31, the surface 31A constituting the secondsurface of the PSA sheet may be subjected to a suitable treatment, suchas a treatment to increase the releasing properties of the surface(formation of a release layer treated with a silicone-based,fluorine-based, long-chain alkyl-based release agent, etc.; polyolefinfilm lamination, etc.), a treatment to increase the non-releasingproperties or printability of the surface (corona discharge treatment,etc.); a treatment to increase the decorativeness of the surface (e.g.printing, metal vapor deposition), and so on.

Configurational Example 4

The art disclosed herein can be preferably practiced, for instance, suchas in PSA sheet 20 shown in FIG. 4, in an embodiment of PSA sheet 2 inthe configuration shown in FIG. 2 where the intermediate layer 23 is abubble-containing layer 223. In other words, PSA sheet 20 shown in FIG.4 is a double-faced PSA sheet comprising a first PSA layer 221constituting the first adhesive face 221A, a second PSA layer 222constituting the second adhesive face 222A and an intermediate layer 223placed between them. The first PSA layer 221 is a bubble-free adhesivelayer formed of an acrylic PSA layer with its surface being the firstadhesive face 221A. The second PSA layer 222 is a bubble-free adhesivelayer formed of an acrylic PSA layer or other PSA layer with its surfacebeing the second adhesive face 222A. The intermediate layer 223 is abubble-containing layer and its first surface 223A and second surface223B are both non-releasable surfaces. The intermediate layer 223 can bea bubble-containing adhesive layer or a bubble-containing non-adhesivelayer. The PSA sheet preferably has, but not particularly limited to, ato-EPDM initial peel strength of 5 N/10 mm or greater when measured atleast with respect to the first adhesive face 221A.

In PSA sheet 20 shown in FIG. 4, the back face (opposite from the firstadhesive face 221A) of the first PSA layer 221 is supported with thefirst surface 223A of the intermediate layer 223. The back face of thesecond PSA layer 222 is supported with the second surface 223B of theintermediate layer 223. In other words, the intermediate layer 223serves as the support layer for the first PSA layer 221 and the secondPSA layer 222.

According to such a PSA sheet in a configuration where the PSA layers221 and 222 are supported with the intermediate layer 223, by preferablycombining the nature of the PSA layers 221 and 222 with the nature ofthe intermediate layer 223, a high performance PSA sheet can be madebenefiting from their individual advantages. Adjustments can be easilymade, for instance, so as to compose the PSA layer 221 constituting anadhesive face with the focus on the adhesion to EPDM and other olefinicrubber surfaces while composing the intermediate layer 223 as thesupport layer with the focus on the cushioning properties and cohesion.With the adhesive face-constituting PSA layers 221 and 222 beingbubble-free layers and the intermediate layer 223 being abubble-containing layer, highly smooth adhesive faces can be combinedwith great cushioning properties of the PSA sheet as a whole at a highlevel. It is also preferable from the standpoint of the quality of theexternal appearance that the adhesive face-constituting PSA layers 221and 222 are bubble-free layers.

Configurational Example 4-1

A preferable example of PSA sheet 20 having a configuration shown inFIG. 4 is a configuration where the first PSA layer 221 is a bubble-freeadhesive layer formed of an acrylic PSA layer, the second PSA layer 222is a bubble-free adhesive layer formed of an acrylic PSA layer or otherPSA layer, and the intermediate layer 223 is a bubble-containingadhesive layer. According to such a configuration, with the intermediatelayer 223 being an adhesive layer, sufficient joining strength can bereadily assured between the intermediate layer 223 and each of the PSAlayers 221 and 222. From the standpoint of the joining strength, anacrylic PSA layer can be preferably used as the intermediate layer 223.It is also preferable from the standpoint of the weatherability of thePSA sheet 20, etc., that the intermediate layer 223 is an acrylic PSAlayer. In an embodiment particularly preferable from the standpoint ofthe weatherability, each of the layers 221, 222 and 223 in the PSA sheet20 is an acrylic PSA layer.

The method for preparing such a PSA sheet 20 is not particularlylimited. It can be preferably produced, for instance, by a methodcomprising a step of preparing a bubble-containing adhesive layer as anintermediate layer 223, a step of preparing two independent PSA layersto form PSA layers 221 and 222, and a step of adhering these PSA layersto the first surface 223A and second surface 223B of the intermediatelayer 223, respectively. In a preferable embodiment of such a productionmethod, the bubble-containing layer and the two independent PSA layersare all allowed to cure with irradiation of active energy rays(typically light such as UV light).

The intermediate layer 223 can be a layer formed of a singlebubble-containing adhesive layer or a layer having a multi-layerstructure (laminate structure) in which multiple bubble-containingadhesive layers are laminated. When the intermediate layer 223 has amulti-layer structure formed of several bubble-containing adhesivelayers, for the individual bubble-containing adhesive layers, thecompositions, bubble contents, thicknesses and so on may be the samewith or different from one another. The number of bubble-containingadhesive layers in the intermediate layer 223 is not particularlylimited. For instance, it can be about 2 to 100 layers. From thestandpoint of the productivity of the PSA sheet, etc., it is usuallysuitably about 2 to 50 layers, and preferably, for instance, about 2 to30 layers.

Configurational Example 4-2

Another preferable example of PSA sheet 20 having a configuration shownin FIG. 4 is a configuration where each of the first PSA layer 221 andthe second PSA layer 222 is a bubble-free adhesive layer formed of anacrylic PSA layer, and the intermediate layer 223 is a bubble-containingnon-adhesive layer. One or each of the surfaces 223A and 223B of theintermediate layer 223 may be subjected to a surface treatment toincrease the non-releasing properties of the surface(s), such as coronadischarge treatment, primer layer formation, etc. In the PSA sheet 20 insuch a configuration, because the intermediate layer 223 is anon-adhesive layer, the intermediate layer (bubble-containing layer) canbe selected from a wider range of materials. It is preferable because,for instance, suitable thickness, bubble content, compression hardness,breaking strength, etc., can be easily selected for the intermediatelayer and this makes it easy to adjust the cushioning properties,repulsion resistance, etc., of the PSA sheet as a whole.

Configurational Example 5

PSA sheet 10 shown in FIG. 5 is an embodiment of PSA sheet 1 accordingto Configurational Example 1 shown in FIG. 1, being a double-faced PSAsheet formed of an acrylic PSA layer as the bubble-containing adhesivelayer 121. The PSA sheet 10 preferably has, but not particularly limitedto, a to-EPDM initial peel strength of 5 N/10 mm or greater whenmeasured about either the first surface (first adhesive face) 121A orthe second surface (second adhesive face) 121B of the bubble-containingadhesive layer 121.

Although not particularly limited to this, PSA sheet 10 in such aconfiguration can be preferably used, similarly to the PSA sheet 1according to Configurational Example 1, in an embodiment where each ofthe first surface (first adhesive face) 121A and the second surface(second adhesive face) 121B of the bubble-containing adhesive layer 121is applied to an olefinic rubber surface such as EPDM. It can bepreferably used also in an embodiment where the first adhesive face 121Ais applied to an olefinic rubber surface and the second adhesive face121B is applied to various types of adherend surface (not limited to anolefinic rubber surface).

The bubble-containing adhesive layer 121 can be a PSA layer formed of asingle acrylic PSA layer or can be a PSA layer having a multi-layerstructure (laminate structure) in which multiple acrylic PSA layers arelaminated. When the bubble-containing adhesive layer 121 is a PSA layerhaving a multi-layer structure formed of several acrylic PSA layers, forthe individual acrylic PSA layers, the compositions, bubble contents,thicknesses and so on can be the same with or different from oneanother. The number of acrylic PSA layers in the bubble-containingadhesive layer 121 is not particularly limited and can be, for instance,about 2 to 100 layers. From the standpoint of the productivity of thePSA sheet, etc., it is usually suitably about 2 to 50 layers, forinstance, preferably about 2 to 30 layers.

Configurational Example 6

PSA sheet 30 shown in FIG. 6 is a double-faced PSA sheet that comprisesa first PSA layer 321 being a bubble-free adhesive layer andconstituting the first adhesive face 321A and a second PSA layer 322being a bubble-containing adhesive layer and constituting the secondadhesive face 322A.

A preferable example of PSA sheet 30 having such a configuration is aconfiguration in which the first PSA layer (bubble-free adhesive layer)321 is an acrylic PSA layer and the first PSA layer 321 is supportedwith the surface 322B of the second PSA layer (bubble-containingadhesive layer) 322. The acrylic PSA layer as the first PSA layer 321 ispreferably a PSA layer (A) described later. The second PSA layer 322 canbe a PSA layer (a) or other PSA layer that is not a PSA layer (A). Forinstance, it is preferable to use a configuration where the second PSAlayer 322 is an acrylic PSA layer other than a PSA layer (A). Althoughnot particularly limited to this, PSA sheet 30 in such a configurationcan be preferably used in an embodiment where, for instance, the firstadhesive face 321A is applied to a low-polar surface such as an olefinicrubber material surface and the second adhesive face 322A is applied tovarious types of adherend surface (not limited to a low-polar surface).

Configurational Example 7

PSA sheet 40 shown in FIG. 7 is an adhesively single-faced PSA sheethaving a PSA layer 421 constituting its first surface (first adhesiveface) 421A and a non-adhesive backside layer 431 constituting the secondsurface 431A. The PSA layer 421 is a bubble-free adhesive layer formedof an acrylic PSA layer. The acrylic PSA layer as PSA layer 421 ispreferably a PSA layer (A) described later. The backside layer (supportlayer) 431 supporting the PSA layer 421 is a bubble-containingnon-adhesive layer in which at least its PSA layer 421—side surface 431Bis non-releasable. As the backside layer 431, a suitable one can beselected among aforementioned various types of foam sheets. Forinstance, a foam sheet formed of a polyolefinic foam body can bepreferably used. While not particularly limited to this, for instance, afoam sheet formed with a polyolefinic foam body can be preferably used.Although not particularly limited to this, PSA sheet (single-faced PSAsheet) 40 thus configured can be preferably used, for instance, in anembodiment where the adhesive face 421A is applied to a surface of alow-polar material such as an olefinic rubber material. The PSA layer421—side surface 431B of the backside layer 431 may be subjected to asurface treatment to increase the non-releasing properties of thesurface, such as corona discharge treatment, primer layer formation,etc. Of the backside layer 431, the surface 431A constituting the secondsurface of the PSA sheet 40 may be subjected to a suitable treatment,such as a treatment to increase the releasing properties of the surface(formation of a release layer treated with a silicone-based,fluorine-based, long-chain alkyl-based release agent, etc.; polyolefinfilm lamination, etc.), a treatment to increase the non-releasingproperties or printability of the surface (corona discharge treatment,etc.); a treatment to increase the decorativeness of the surface (e.g.printing, metal vapor deposition), and so on.

In the respective PSA sheets exemplified in FIGS. 1 to 7, the layersshown in the respective drawings may have each a single-layer structureor multi-layer structure (i.e. a structure including multiple layers).It may further have another layer (a primer layer, release layer,colored layer such as a printed layer, deposited metal layer, antistaticlayer, surface-protective layer) on the surface other than the adhesiveface or between the respective layers.

Prior to use (i.e. before applied to an adherend), a PSA sheet disclosedherein may be in an embodiment where its adhesive face is protected witha release liner having a release face at least on the adhesive faceside. Alternatively, for instance, PSA sheet 3 shown in FIG. 3 may be inan embodiment where the surface 31A of backside layer 31 is a releaseface and PSA sheet 3 is wound so that the adhesive face 21A is incontact and protected with the surface 31A.

<Acrylic PSA Layer>

The PSA sheet disclosed herein has an adhesive face constituted with anacrylic PSA layer. There are no particular limitations to thecomposition or structure of the acrylic PSA layer constituting theadhesive face. The PSA sheet according to a preferable embodiment has apeel strength (20-min peel strength to standard EPDM plate) of 5 N/10 mmor greater when measured by directly applying the adhesive face to anEPDM surface.

Preferable embodiments are described next about the acrylic PSA layerconstituting an adhesive face in the PSA sheet disclosed herein. Thescope of the present invention is not to be limited by this.

[Amino Group-Containing (Meth)Acrylate (Monomer A)]

The acrylic PSA layer constituting an adhesive face of the PSA sheetdisclosed herein typically comprises an acrylic polymer. The concept ofpolymer referred to herein encompasses a polymer having a relatively lowdegree of polymerization, which may be generally called an oligomer.

In a preferable acrylic PSA layer disclosed herein, the acrylic polymercomprises an amino group-containing (meth)acrylate (or a “monomer A”hereinafter) as its monomeric component. In other words, an acrylic PSAlayer comprising a monomer unit derived from the monomer A ispreferable. The monomeric components may comprise one species of suchamino group-containing (meth)acrylate or may comprise two or more suchspecies in combination. In this description, an acrylic PSA layercomprising a monomer A-derived monomer unit is sometimes regarded as a“PSA layer (A).”

Herein, the amino group-containing (meth)acrylate refers to a(meth)acrylate having at least one amino group per molecule. From thestandpoint of the polymerization reactivity, etc., a preferable aminogroup-containing (meth)acrylate usually has one amino group permolecule.

The amino group in the amino group-containing (meth)acrylate can be anyamong a primary amino group (—NH₂), secondary amino group (—NHR^(a)),tertiary amino group (—NR^(a)R^(b)) and quaternary ammonium group(—N±R^(a)R^(b)R^(c)). Herein, R^(a), R^(b) and R^(c) are monovalentorganic groups that are identical to or different from one another andmay be coupled to one another to form a ring structure. For instance,R^(a), R^(b) and R^(c) may have each about 1 to 20 carbon atoms. Fromthe standpoint of the polymerization reactivity, it is usuallypreferable to use an amino group-containing (meth)acrylate wherein eachof R^(a), R^(b) and R^(c) is a hydrocarbon group having about 1 to 20carbon atoms. In particular, an amino group-containing (meth)acrylatehaving a tertiary amino group wherein R^(a) and R^(b) are each a(cyclo)alkyl group having about 1 to 20 carbon atoms (e.g. anN,N-dialkylaminoalkyl (meth)acrylate) is preferable.

The concept of amino group in the amino group-containing (meth)acrylatedoes not include a species in which the amino nitrogen constitutes anamide group. Accordingly, amide group-containing (meth)acrylates such asacrylamide and acryloylmorpholine are not included in the aminogroup-containing (meth)acrylate (monomer A) referred to herein. On theother hand, a (meth)acrylate having at least one amino group that doesnot constitute an amide group and further has an amide group in additionto the amino group may belong to the amino group-containing(meth)acrylate referred to herein.

In a preferable embodiment of the art disclosed herein, the acrylicpolymer may comprise an amino group-containing (meth)acrylate (monomerA) represented by the following formula (1):

CH₂═CR¹COO(CH₂)_(n)NR²R³  (1)

In the formula (1), R¹ can be a hydrogen atom or methyl group and n canbe 0 to 6 (typically 0 to 4, preferably 1 to 3). R² and R³ can be eachindependently selected from a hydrogen atom and a hydrocarbon group.Preferable examples of the hydrocarbon group include an acyclic alkylgroup having 1 to 20 carbon atoms and a cycloalkyl group having 4 to 20carbon atoms. Examples of a hydrocarbon group preferable from thestandpoint of the polymerization reactivity include an acyclic alkylgroup having 1 to 16 carbon atoms (e.g. 1 to 12 carbon atoms, typically1 to 10 carbon atoms) and a cycloalkyl group having 4 to 16 carbon atoms(e.g. 4 to 12 carbon atoms, typically 4 to 10 carbon atoms). The acyclicalkyl group can be linear or branched. In particular, an acyclic alkylgroup having 1 to 4 (more preferably 1 to 3, typically 1 to 2) carbonatoms is preferable.

Specific examples of the amino group-containing (meth)acrylaterepresented by the formula (1) include N,N-dialkylaminoalkyl(meth)acrylates such as N,N-dimethylaminomethyl (meth)acrylate,N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl(meth)acrylate, N,N-dimethylaminobutyl (meth)acrylate,N,N-dimethylaminohexyl (meth)acrylate, N,N-diethylaminoethyl(meth)acrylate, N,N-dipropylaminoethyl (meth)acrylate,N,N-dibutylaminoethyl (meth)acrylate, N-methyl-N-ethylaminoethyl(meth)acrylate, N-methyl-N-butylaminoethyl (meth)acrylate, andN,N-dipropylaminopropyl (meth)acrylate; N-alkylaminoalkyl(meth)acrylates such as N-methylaminoethyl (meth)acrylate,N-ethylaminoethyl (meth)acrylate, N-isopropylaminoethyl (meth)acrylate,N-t-butylethyl (meth)acrylate and N-butylaminoethyl (meth)acrylate;N-alkylamino(meth)acrylates such as N-methylamino(meth)acrylate andN-ethylamino(meth)acrylate; N,N-dialkylamino(meth)acrylates such asN,N-dimethylamino(meth)acrylate and N,N-diethylamino(meth)acrylate;aminoethyl (meth)acrylate aminoalkyl (meth)acrylates such as aminomethyl(meth)acrylate; amino(meth)acrylates; and the like.

Examples of the amino group-containing (meth)acrylate having aquaternary ammonium group include a quaternary alkyl halide of an aminogroup-containing (meth)acrylate having a tertiary amino group, forexample, a quaternary alkyl halide of an N,N-dialkylaminoalkyl(meth)acrylate. Specific examples include dimethylaminoethyl acrylatemethyl chloride quaternary salt and dimethylaminoethyl methacrylatemethyl chloride quaternary salt.

Among these, preferable amino group-containing (meth)acrylates includeN,N-dimethylaminoethyl acrylate (or “DMAEA” hereinafter),N,N-dimethylaminoethyl methacrylate (or “DMAEM” hereinafter),N,N-diethylaminoethyl acrylate and N,N-diethylaminoethyl methacrylate.In particular, DMAEA and DMAEM are preferable. DMAEM is especiallypreferable in view that the peel strength is unlikely to decrease evenwith time after applied to a low-polar surface (e.g. a surface formedfrom an olefinic rubber material) or the peel strength may furtherincrease.

[Monomer(s) Other than Amino Group-Containing (Meth)Acrylate (MonomerB)]

In addition to the amino group-containing (meth)acrylate (monomer A),the acrylic PSA layer may comprise, as a monomeric component of thepolymer in the acrylic PSA layer, a monomer (or “monomer B” hereinafter)other than the amino group-containing (meth)acrylate. The monomer B canbe an acrylic monomer or a non-acrylic monomer (e.g. a monomer having anethylenic unsaturated group other than a (meth)acryloyl group).

Preferable examples of an acrylic monomer that can be used as themonomer B include a (cyclo)alkyl (meth)acrylate (or “monomer B”hereinafter). For instance, a (cyclo)alkyl (meth)acrylate represented bythe following formula (2) is preferable.

CH₂═CR⁴COOR⁵  (2)

In the formula (2), R⁴ is a hydrogen atom or methyl group. R⁵ is a(cyclo)alkyl group and can be typically a acyclic alkyl group having 1to 20 carbon atoms or a cycloalkyl group having 4 to 20 carbon atoms.From the standpoint of the PSA's storage modulus, etc., it is preferableto use a (cyclo)alkyl (meth)acrylate wherein R⁵ is an acyclic alkylgroup having 1 to 16 (e.g. 1 to 12, typically 1 to 10) carbon atoms or acycloalkyl group having 4 to 16 (e.g. 4 to 12, typically 4 to 10) carbonatoms. When R⁵ is an acyclic alkyl group, the alkyl group can be linearor branched.

Examples of an alkyl (meth)acrylate with R⁵ being a C₁₋₂₀ acyclic alkylgroup include methyl (meth)acrylate, ethyl (meth)acrylate, propyl(meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate,isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate,pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate,heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl(meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl(meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl(meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate,tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl(meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate,nonadecyl (meth)acrylate, eicosyl (meth)acrylate, etc. Examples of acycloalkyl (meth)acrylate with R⁵ being a C₄₋₂₀ cycloalkyl group includecyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl(meth)acrylate, etc. These can be used singly as one species or in acombination of two or more species.

Examples of a particularly preferable (cyclo)alkyl (meth)acrylateinclude n-butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), laurylacrylate, lauryl methacrylate, t-butyl acrylate, cyclohexyl acrylate(CHA), cyclohexyl methacrylate (CHMA), isobornyl acrylate (IBXA),isobornyl methacrylate (IBXMA), etc. These can be used singly as onespecies or in a combination of two or more species.

The monomeric components of the polymer in the acrylic PSA layer maycomprise a monomer (or “monomer B2” hereinafter) other than a(cyclo)alkyl (meth)acrylate. Such a monomer can be used to increasevarious properties such as cohesion, heat resistance, tightness ofadhesion, etc.

Examples of the monomer B2 include a monomer having a functional group(or a “functional group-containing monomer” hereinafter). Such afunctional group-containing monomer can be added to introducecrosslinking points in the polymer in the acrylic PSA layer so as toincrease the cohesive strength of the acrylic PSA. Examples of suchfunctional group-containing monomers include:

carboxy group-containing monomers including ethylenic unsaturatedmono-carboxylic acids such as acrylic acid, methacrylic acid, crotonicacid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, etc.;and ethylenic unsaturated dicarboxylic acids such as itaconic acid,maleic acid, fumaric acid, citraconic acid, etc., as well as metal saltsthereof (e.g. alkali metal salts);

acid anhydride group-containing monomers including acid anhydrides suchas maleic acid anhydride, itaconic acid anhydride, etc.;

hydroxy group-containing monomers including hydroxyalkyl (meth)acrylatessuch as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate,3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate,4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate,8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate,12-hydroxylauryl (meth)acrylate (4-hydroxymethylcyclohexyl)methyl(meth)acrylate, etc.; as well as unsaturated alcohols such as N-methylol(meth)acrylamide, vinyl alcohol, allyl alcohol, 2-hydroxyethyl vinylether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether,etc.;

amide group-containing monomers including (meth)acrylamide,N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide,N-methylol(meth)acrylamide, N-methylolpropane(meth)acrylamide,N-methoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide;

cyano group-containing monomers such as acrylonitrile,methacrylonitrile, etc.;

sulfonic acid group-containing monomers such as styrene sulfonic acid,allyl sulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid(meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate(meth)acryloyloxy naphthalene sulfonic acid, etc.;

phosphoric acid group-containing monomers such as 2-hydroxyethylacryloyl phosphate, etc.;

oxazoline group-containing monomers such as 2-vinyl-2-oxazoline,2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, etc.;

aziridine group-containing monomers such as (meth)acryloylaziridine and2-aziridinylethyl (meth)acrylate;

epoxy group (glycidyl group)-containing monomers such as glycidyl(meth)acrylate, methylglycidyl (meth)acrylate, allyl glycidyl ether,etc.;

keto group-containing monomers such as diacetone (meth)acrylamide,diacetone (meth)acrylate, vinyl methyl ketone, allyl acetoacetate, vinylacetoacetate, etc.;

isocyanate group-containing monomers such as 2-(meth)acryloyloxyethylisocyanate, etc.;

alkoxy group-containing monomers such as methoxyethyl (meth)acrylate,ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, butoxyethyl(meth)acrylate, ethoxypropyl (meth)acrylate, etc.;

alkoxysilyl group-containing monomers such as3-(meth)acryloxypropyltrimethoxysilane,3-(meth)acryloxypropyltriethoxysilane,3-(meth)acryloxypropylmethyldimethoxysilane,3-(meth)acryloxypropylmethyldiethoxysilane, etc.; and so on.

Other examples include a macro monomer having a radically-polymerizablevinyl group in a terminal monomer unit of a vinyl polymer, etc. Thesecan be used singly as one species or in combination of two or morespecies.

To adjust the glass transition temperature (Tg) or to increase thecohesive strength, etc., the monomeric components may include a monomerother than the functional group-containing monomers listed above.Examples of such a monomer B2 include:

carboxylic acid vinyl esters such as vinyl acetate, vinyl propionate,vinyl lactate, vinyl pivalate, vinyl cyclohexane carboxylate, vinylbenzoate, etc.;

aromatic vinyl compounds such as styrene, substituted styrenes(α-methylstyrene, etc.), vinyl toluene, etc.;

aromatic ring-containing (meth)acrylates such as aryl (meth)acrylates(e.g. phenyl (meth)acrylate), aryloxyalkyl (meth)acrylates (e.g.phenoxyethyl (meth)acrylate), arylalkyl (meth)acrylates (e.g. benzyl(meth)acrylate), etc.;

nitrogen atom-containing rings such as N-vinyl-2-pyrrolidone,N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone,N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole,N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam,N-(meth)acryloyl morpholine, etc.;

olefinic monomers such as ethylene, propylene, isoprene, butadiene,isobutylene, etc.;

chlorine-containing monomers such as vinyl chloride, vinylidenechloride, etc.;

vinyl ether-based monomers such as methyl vinyl ether, ethyl vinylether, etc.; and the like.

These can be used singly as one species or in combination of two or morespecies.

The monomeric components may comprise, as a monomer B2, a polyfunctionalmonomer for crosslinking and so on, if necessary. Examples of such apolyfunctional monomer include monomers having two or more polymerizablefunctional groups (typically (meth)acryloyl groups) per molecule, suchas 1,6-hexanediol di(meth)acrylate, ethylene glycol di(meth)acrylate,propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate,polypropylene glycol di(meth)acrylate, neopentyl glycoldi(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropanetri(meth)acrylate, ethyleneoxide-modified trimethylolpropanetri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritolpenta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, etc. Thesecan be used singly as one species or in combination of two or morespecies. From the standpoint of the reactivity, etc., it is usuallypreferable to use a polyfunctional monomer having two or more (typicallythree or more) acryloyl groups per molecule.

[Composition of all Monomer Components]

The ratio of acrylic monomer to all monomeric components of the totalpolymer (or “all monomeric components” hereinafter) in the acrylic PSAlayer is typically higher than 50% by mass and can be preferably 70% bymass or higher, more preferably 85% by mass or higher (e.g. 90% by massor higher). The ratio of mass of acrylic monomer to mass (m_(T)) of allmonomeric components can be essentially 100% by mass (e.g. 98% to 100%by mass). The ratio of acrylic polymer to mass of entire acrylic PSAlayer is typically 70% by mass or higher and can be preferably 80% bymass or higher (90% by mass or higher).

When the acrylic PSA layer comprises an amino group-containing(meth)acrylate (monomer A) as its monomeric component, the ratio(m_(A)/m_(T)) of mass (m_(A)) of monomer A to mass (m_(T)) of allmonomeric components of the acrylic PSA layer can be, for instance,higher than 0.2% by mass (typically higher than 0.5% by mass). From thestandpoint of the adhesion to a low-polar material such as an olefinicrubber material, the monomer A content is preferably higher than 1.0% bymass or more preferably higher than 2.0% by mass.

In a preferable embodiment, the amino group-containing (meth)acrylate(monomer A) can be included at a ratio higher than 2.6% by mass of allmonomeric components of the acrylic PSA layer. In other words, theacrylic PSA layer in the art disclosed herein preferably comprises amonomer A-derived monomer unit at a ratio higher than 2.6% by mass ofall polymers in the acrylic PSA layer (typically at a ratio higher than2.6% by mass of the entire acrylic PSA layer). The acrylic PSA layerhaving such a composition may provide great adhesion to an adherendformed of an olefinic rubber material and other low-polar adherend. Fromthe standpoint of the adhesion, etc., the ratio (m_(A)/m_(T)) of mass(m_(A)) of monomer A to mass (m_(T)) of all monomeric components ispreferably higher than 5% by mass, more preferably 6% by mass or higher,or yet more preferably 7% by mass or higher. The upper limit ofm_(A)/m_(T) is not particularly limited. From the standpoint of thepolymerization reactivity, initial adhesiveness, etc., it is usuallysuitably 80% by mass or lower, preferably 60% by mass or lower, morepreferably 50% by mass or lower, or typically lower than 50% by mass. Inan embodiment where an active energy ray-curing (e.g. UV-curing) PSAcomposition is used to form the acrylic PSA layer, from the standpointof the curing properties of the PSA composition, m_(A)/m_(T) is suitably30% by mass or lower, or preferably 25% by mass or lower (e.g. 20% bymass or lower).

The curing properties of the PSA composition with active energy rays canbe thought as the ease of forming acrylic PSA from the PSA compositionand further as the productivity of a PSA sheet having the acrylic PSA.Hereinafter, curing properties with active energy rays are sometimesreferred to simply as “curing properties.”

The art disclosed herein can be preferably implemented in an embodimentwhere the acrylic PSA layer comprises a (cyclo)alkyl (meth)acrylate(monomer B1) at a ratio higher than 50% by mass (typically at a ratio ofhigher than 50% by mass, but lower than 97.4% by mass or lower) ofm_(T). Such an embodiment can combine adhesion to low-polar materialssuch as olefinic rubber materials and polymerization reactivity at ahigh level. High polymerization reactivity is advantageous in terms ofthe ease of acrylic PSA layer formation (and further the productivity ofthe PSA sheet having the acrylic PSA layer). From the standpoint of thepolymerization reactivity, the ratio of mass of monomer B1 to m_(T) canbe, for instance, higher than 50% by mass, but 97% by mass or lower; orit is more preferably lower than 96% by mass, more preferably 95% bymass or lower, or yet more preferably 94% by mass or lower (even 93% bymass lower).

The art disclosed herein can be preferably implemented in an embodimentwhere the monomeric components of the acrylic PSA layer comprise anacyclic alkyl (meth)acrylate as the monomer B1. With the use of theacyclic alkyl (meth)acrylate, a PSA sheet can be obtained having greatinitial adhesion to various types of adherend. The ratio of mass ofacyclic alkyl (meth)acrylate to m_(T) can be, for instance, 20% by massor higher, or it is usually suitably 30% by mass or higher, preferably40% by mass or higher, or more preferably 50% by mass or higher(typically higher than 50% by mass). From the standpoint of thecohesion, etc., the ratio is usually suitably 95% by mass or lower, orpreferably 90% by mass or lower (e.g. 80% by mass or lower).

The art disclosed herein can be preferably implemented in an embodimentwhere the monomeric components of the acrylic PSA layer comprise acycloalkyl (meth)acrylate as the monomer B1. With the use of thecycloalkyl (meth)acrylate, adhesion to a low-polar material such as anolefinic rubber material can be combined with cohesion of the PSA at ahigher level. When the monomeric components of the acrylic PSA layercomprises a cycloalkyl (meth)acrylate, the ratio (m_(C)/m_(T)) of mass(m_(C)) of cycloalkyl (meth)acrylate to m_(T) can be, for instance, 1%by mass or higher. From the standpoint of obtaining greater effects ofthe use of the cycloalkyl (meth)acrylate, m_(C)/m_(T) is suitably 5% bymass or higher, preferably 10% by mass or higher, or more preferably 15%by mass or higher (e.g. 20% by mass or higher, or even 25% by mass orhigher). From the standpoint of the polymerization reactivity, etc.,m_(C)/m_(T) is usually suitably less than 50% by mass, preferably 40% bymass or less, or more preferably 35% by mass or less (e.g. 30% by massor less).

When the monomeric components of the acrylic PSA layer comprise a cyclo(meth)acrylate, the ratio (m_(A)/m_(C)) of mass (m_(A)) of monomer A tomass (m_(C)) of cyclo (meth)acrylate is not particularly limited in allmonomeric components of the PSA layer. From the standpoint of theadhesion to a low-polar surface such as an olefinic rubber surface, theratio (m_(A)/m_(C)) value is effectively 0.20 or higher (typicallyhigher than 0.20), preferably 0.22 or higher, or more preferably 0.24 orhigher. From the standpoint of combining adhesion to an olefinic rubbersurface and cohesion at a higher level, the ratio (m_(A)/m_(C)) value ispreferably 0.30 or higher and can be, for example, 0.35 or higher. Theupper limit of the ratio (m_(A)/m_(C)) value is not particularlylimited. From the standpoint of the polymerization reactivity, etc., itis usually suitably 0.70 or lower, preferably 0.65 or lower, or morepreferably 0.50 or lower.

When the entire monomeric components in the acrylic PSA layer compriseboth the acyclic alkyl (meth)acrylate and cycloalkyl (meth)acrylate asthe monomer B1, the ratio of mass of acyclic alkyl (meth)acrylate tom_(T) can be, for instance, higher than 50% by mass, but 85% by mass orlower, or preferably 55% by mass or higher, but 85% by mass or lower(e.g. 55% by mass or higher, but 70% by mass or lower). In view of thebalance between adhesion and cohesion, polymerization reactivity, etc.,the mass ratio (acyclic alkyl (meth)acrylate/cycloalkyl (meth)acrylate)of acrylic alkyl (meth)acrylate to cycloalkyl (meth)acrylate in allmonomeric components can be, for instance, 1.5 to 10, preferably 1.7 to5.5, or more preferably 1.8 to 3.5 (e.g. 2.0 to 3.0).

When the monomeric components of the acrylic PSA layer comprise amonomer B2, its content can be, for instance, 30% by mass or less ofm_(T). From the standpoint of the adhesion to a low-polar material suchas an olefinic rubber material, the monomer B2 content is suitably 20%by mass or less of m_(T), preferably 10% by mass or less, or morepreferably 5% by mass or less (e.g. 2% by mass or less).

The art disclosed herein can be preferably implemented in an embodimentwhere the ratio of mass of carboxy group-containing monomer to m_(T) is0 to 1% by mass (more preferably 0 to 0.5% by mass, yet more preferably0 to 0.1% by mass). Herein, the ratio of mass of carboxygroup-containing monomer to m_(T) being 0 means that no carboxygroup-containing monomer is used at least intentionally. An acrylic PSAlayer having such a composition contains very little to no carboxygroup. Thus, its surface (adhesive face) may be low polar. This mayadvantageously contribute to increase the adhesion to a low-polarmaterial such as an olefinic rubber material. Better results can beobtained when the combined ratio of mass of carboxy group-containingmonomer and mass of hydroxy group-containing monomer to m_(T) is 0 to 1%by mass (more preferably 0 to 0.5% by mass, even more preferably 0 to0.1% by mass).

The art disclosed herein can be preferably implemented, for instance, inan embodiment where a polyfunctional monomer is included as the monomerB2 in the entire monomeric components of the acrylic PSA layer. Theamount of the polyfunctional monomer used can be, for instance, 2% bymass or less (typically 0.01 to 1% by mass, preferably 0.02 to 1% bymass, or more preferably 0.05 to 0.5% by mass) of m_(T). In a preferableembodiment, a polyfunctional monomer is included solely as the monomerB2. Another preferable embodiment is essentially free of the monomer B2.

The composition of all monomeric components of the acrylic PSA layer canbe formulated so as to yield a glass transition temperature (Tg) of itscompletely polymerized product of −60° C. or higher, but −10° C. orlower. From the standpoint of the initial adhesion to an adherend (e.g.a low-polar material such as an olefinic rubber material), the Tgdetermined from the composition of all monomeric components of theacrylic PSA layer (i.e. Tg of the completely polymerized product of allmonomeric components) is suitably −15° C. or lower, preferably −20° C.or lower, or more preferably −25° C. or lower. From the standpoint ofthe cohesion of the PSA, the Tg is suitably −60° C. or higher,preferably −55° C. or higher, or more preferably −50° C. or higher. In apreferable embodiment of the art disclosed herein, the Tg determinedfrom the composition of all monomeric components can be, for instance,−50° C. to −30° C. (typically −45° C. to −30° C.).

Herein, the Tg of a polymer refers to a value determined by the Foxequation based on the Tg values of homopolymers of the respectivemonomers constituting the polymer and mass fractions (copolymer ratio bymass) of the monomers. Thus, the Tg of the polymer can be adjusted bysuitably modifying the monomer composition (i.e. types and relativeamounts of monomers used for the synthesis of the acrylic polymer).

As the Tg values of the homopolymers, values given in a known documentare used:

2-ethylhexyl acrylate −70° C. n-butyl acrylate −55° C. ethyl acrylate−22° C. methyl acrylate 8° C. methyl methacrylate 105° C. cyclohexylacrylate 15° C. cyclohexyl methacrylate 66° C. isobornyl acrylate 94° C.isobornyl methacrylate 180° C. N,N-dimethylaminoethyl acrylate 18° C.N,N-dimethylaminoethyl methacrylate 18° C. N,N-diethylaminoethylacrylate 20° C. N,N-diethylaminoethyl methacrylate 20° C. vinyl acetate32° C. 2-hydroxyethyl acrylate −15° C. styrene 100° C. acrylic acid 106°C. methacrylic acid 228° C.

With respect to the Tg values of homopolymers other than the exampleslisted above, the values given in “Polymer Handbook” (3rd edition, JohnWiley & Sons, Inc., Year 1989) are used.

When no values are given in “Polymer Handbook” (3rd edition, John Wiley& Sons, Inc., Year 1989), values obtained by the following measurementmethod are used (see Japanese Patent Application Publication No.2007-51271).

In particular, to a reaction vessel equipped with a thermometer, astirrer, a nitrogen inlet and a condenser, are added 100 parts by weightof monomer(s), 0.2 part by weight of azobisisobutyronitrile, and 200parts by weight of ethyl acetate as a polymerization solvent, and themixture is stirred for one hour under a nitrogen gas flow. After oxygenis removed in this way from the polymerization system, the mixture isheated to 63° C. and the reaction is carried out for 10 hours. Then, itis cooled to room temperature, and a homopolymer solution having 33% bymass solid content is obtained. Subsequently, this homopolymer solutionis applied onto a release liner by flow coating and allowed to dry toprepare a test sample (a homopolymer sheet) of about 2 mm thickness.This test sample is cut out into a disc of 7.9 mm diameter and is placedbetween parallel plates; and while applying a shear strain at afrequency of 1 Hz using a rheometer (ARES, available from RheometricsScientific, Inc.), the viscoelasticity is measured in the shear modeover a temperature range of −70° C. to 150° C. at a heating rate of 5°C./min; and the temperature value at the maximum of the tan 6 curve istaken as the Tg of the homopolymer.

<PSA Composition>

The acrylic PSA layer in the art disclosed herein may be formed with anacrylic PSA composition that comprises all of its monomeric componentshaving a composition as described above as a polymerized product,non-polymerized product (i.e. in a form where the polymerizablefunctional group is unreacted) or a mixture of these. The PSAcomposition can be in various forms such as a solvent-based PSAcomposition containing the PSA (adhesive component(s)) in an organicsolvent, a water-dispersed PSA composition containing the PSA dispersedin an aqueous solvent, an active energy ray-curable PSA compositionformulated so as to cure with active energy rays such as UV rays andradioactive rays to form PSA, a hot-melt PSA composition which isapplied in a heat-melted state and forms PSA when it cools to near roomtemperature, and the like.

The acrylic PSA composition according to a preferable embodimentpreferably comprises a polymerization product of a monomer mixture. Themonomer mixture (i.e. the monomeric components in the polymerizationproduct) comprises at least part of its entire monomeric components.Thus, the polymerization product of the monomer mixture includes atleast part of the entire monomeric components in a polymerized form (asa polymer). The acrylic PSA composition comprising at least part of theentire monomeric components as a polymer is advantageous in view of thehandling properties (e.g. ease of application, storability) of thecomposition and the adhesive properties, etc.

The polymerization product of the monomer mixture can be prepared byallowing the monomer mixture to undergo polymerization at leastpartially. The method for polymerizing the monomer mixture is notparticularly limited. Various heretofore known polymerization methodscan be suitably employed. For instance, a suitable method can be usedamong solution polymerization, emulsion polymerization, thermalpolymerization (which is typically carried out in the presence of athermal polymerization initiator) such as bulk polymerization,photopolymerization carried out by irradiating light such as UV light(typically in the presence of a photopolymerization initiator),radiation-induced polymerization carried out by irradiating radioactiverays such as β rays and γ rays, and the like. In particular, thephotopolymerization is preferable.

The embodiment of the polymerization is not particularly limited and canbe carried out by suitably selecting a heretofore known monomer supplymethod, polymerization conditions (temperature, pressure, intensity oflight irradiation, intensity of radioactive ray irradiation, etc.),other materials (polymerization initiator, surfactant, etc.) besides themonomers, and so on. For example, as the monomer supply method, theentire monomer mixture can be supplied to a reaction vessel at once(all-at-once supply) or gradually dropwise (continuous supply), or itcan be divided in some portions and the respective portions can besupplied every certain time interval (portionwise supply). The monomermixture can be supplied as a solution or dispersion in which it ispartially or entirely dissolved in a solvent or emulsified in water.

For the polymerization of the monomer mixture, depending on the methodand embodiment of the polymerization, one, two or more species can besuitably selected and used among known or commonly-used polymerizationinitiators.

[Thermal Polymerization Initiator]

The initiator for thermal polymerization is not particularly limited.For example, an azo-based polymerization initiator, peroxide-basedpolymerization initiator, a redox-based polymerization initiator bycombination of a peroxide and a reducing agent, a substitutedethane-based polymerization initiator, and so on can be used. Thermalpolymerization can be preferably carried out at a temperature of, forinstance, about 20° C. to 100° C. (typically 40° C. to 80° C.).

Examples of the azo-based initiator include 2,2′-azobisisobutyronitrile(AIBN), 2,2′-azobis(2-methylpropionamidine) disulfate,2,2′-azobis(2-amidinopropane) dihydrochloride,2,2′-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride,2,2′-azobis(N,N′-dimethyleneisobutylamidine),2,2′-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate,2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile),2,2′-azobis(2,4-dimethylvaleronitrile),2,2′-azobis(2-methylbutyronitrile),1,1′-azobis(cyclohexane-1-carbonitrile),2,2′-azobis(2,4,4-trimethylpentane),dimethyl-2,2′-azobis(2-methylpropionate), etc.

Examples of the peroxide-based initiator include persulfates such aspotassium persulfate, ammonium persulfate, etc., as well as benzoylperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, t-butyl peroxidebenzoate, dicumyl peroxide,1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane,1,1-bis(t-butylperoxy)cyclododecane, hydrogen peroxide, etc.

Examples of the redox-based initiator include a combination of aperoxide and ascorbic acid (combination of hydrogen peroxide water andascorbic acid, etc.), combination of a peroxide and an iron(II) salt(combination of hydrogen peroxide water and an iron(II) salt, etc.),combination of a persulfate salt and sodium hydrogen sulfite, etc.

Specific examples of the substituted ethane-based initiator includephenyl-substituted ethanes, etc.

[Photopolymerization Initiator]

For photopolymerization, various photopolymerization initiators can beused. The photopolymerization initiator is not particularly limited. Forexample, a ketal-based photopolymerization initiator, acetophenone-basedphotopolymerization initiator, benzoin ether-based photopolymerizationinitiator, acylphosphine oxide-based photopolymerization initiator,α-ketol-based photopolymerization initiator, aromatic sulfonylchloride-based photopolymerization initiator, photoactive oxime-basedphotopolymerization initiator, benzoin-based photopolymerizationinitiator, benzil-based photopolymerization initiator,benzophenone-based photopolymerization initiator, thioxanthone-basedphotopolymerization initiator or the like can be used.

Specific examples of the ketal-based photopolymerization initiatorinclude 2,2-dimethoxy-1,2-diphenylethane-1-one (e.g. trade name“IRGACURE 651” available from BASF Japan Ltd.), etc.

Specific examples of the acetophenone-based photopolymerizationinitiator include 1-hydroxycyclohexyl phenyl ketone (e.g. trade name“IRGACURE 184” available from BASF Japan Ltd.),4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone,1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (e.g.trade name “IRGACURE 2959” available from BASF Japan Ltd.),2-hydroxy-2-methyl-1-phenyl-propane-1-one (e.g. trade name “DAROCUR1173” available from BASF Japan Ltd.), etc.

Specific examples of the benzoin ether-based photopolymerizationinitiator include benzoin ethers such as benzoin methyl ether, benzoinethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoinisobutyl ether, etc., as well as substituted benzoin ethers such asanisole methyl ether, etc.

Specific examples of the acylphosphine oxide-based photopolymerizationinitiator include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (e.g.trade name “IRGACURE 819” available from BASF Japan Ltd.),bis(2,4,6-trimethylbenzoyl)-2,4-di-n-butoxyphenylphosphine oxide,2,4,6-trimethylbenzoyldiphenylphosphine oxide (e.g. trade name “LUCIRINTPO” available from BASF Japan Ltd.),bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, etc.

Specific examples of the α-ketol-based photopolymerization initiatorinclude 2-methyl-2-hydroxypropiophenone,1-[4-(2-hydroxyethyl)phenyl]-2-methylpropane-1-one, etc. Specificexamples of aromatic sulfonyl chloride-based photopolymerizationinitiators include 2-naphthalenesulfonyl chloride, etc. Specificexamples of the photoactive oxime-based photopolymerization initiatorinclude 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime, etc.Specific examples of the benzoin-based photopolymerization initiatorinclude benzoin, etc. Specific examples of the benzil-basedphotopolymerization initiator include benzil, etc.

Specific examples of the benzophenone-based photopolymerizationinitiator include benzophenone, benzoylbenzoic acid,3,3′-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone,α-hydroxycyclohexylphenylketone, etc.

Specific examples of the thioxanthone-based photopolymerizationinitiator include thioxanthone, 2-chlorothioxanthone,2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone,2,4-dichlorothioxanthone, 2,4-diethylthioxanthone,isopropylthioxanthone, 2,4-diisopropylthioxanthone, dodecylthioxanthone,etc.

Such thermal polymerization initiator or photopolymerization initiatorcan be used in a typical amount in accordance with the polymerizationmethod or embodiment, etc., without particular limitations. For example,to 100 parts by mass of the monomer mixture, the initiator can be 0.001to 5 parts by mass (typically, 0.01 to 2 parts by mass, e.g. 0.01 to 1part by mass).

<Polymerization Product (a)>

In a preferable embodiment of the art disclosed herein, the PSAcomposition may comprise a polymerization product (a) of the monomermixture comprising an acyclic alkyl (meth)acrylate. The ratio of acyclicalkyl (meth)acrylate in the monomer mixture can be, for instance, 20% bymass or higher, usually suitably 40% by mass or higher, or preferably50% by mass or higher. From the standpoint of the polymerizationreactivity, etc., the ratio of acyclic alkyl (meth)acrylate in themonomer mixture is preferably higher than 50% by mass, more preferably55% by mass or higher, or even more preferably 60% by mass or higher(e.g. higher than 60% by mass). From the standpoint of the adhesion to alow-polar material such as an olefinic rubber material and the cohesion,etc., the ratio is usually suitably 98% by mass or lower, preferably 95%by mass or lower, or more preferably 90% by mass or lower (e.g. 85% bymass or lower, typically 80% by mass or lower).

The monomer mixture typically has a composition corresponding to themonomeric components of the polymerization product (a). The monomermixture may comprise at least some of the amino group-containing(meth)acrylate (monomer A) that is included in the entire monomericcomponents of the PSA layer. The monomer A included in the entiremonomeric components can be included entirely in the monomer mixture.Alternatively, the monomer mixture may be free of the monomer A and themonomer A may be included in a portion other than the monomer mixture(e.g. in the monomeric components of an acrylic oligomer (b) describedlater) among the entire monomeric components.

When the monomer mixture comprises a monomer A, the monomer A content inthe monomer mixture can be, for instance, greater than 0.2% by mass.From the standpoint of obtaining greater effects of the monomer A, itscontent is suitably 0.5% by mass or greater, preferably 0.7% by mass orgreater, or more preferably 1.0% by mass or greater (e.g. 1.2% by massor greater). From the standpoint of increasing adhesion to a low-polarmaterial such as an olefinic rubber material, the monomer A content canbe 1.5% by mass or greater (typically greater than 1.5% by mass), 2.0%by mass or greater, or even 3.0% by mass or greater. The upper limit ofthe monomer A content in the monomer mixture is not particularlylimited. From the standpoint of the polymerization reactivity andinitial adhesion, etc., for instance, it can be 20% by mass or less, andit is usually suitably 17% by mass or less, preferably 15% by mass orless, or more preferably 12% by mass or less (e.g. 10% by mass or less).

The polymerization product (a) can be a resultant obtained bypolymerizing the monomer mixture at least partially. In other words, thepolymerization product (a) can be a partially-polymerized product or acompletely-polymerized product of the monomer mixture. The conversion(monomer conversion) of the polymerization product (a) is notparticularly limited. Thus, the polymerization product (a) may includeunreacted (non-polymerized) monomers or may be essentially free ofthese. Herein, to be essentially free of unreacted monomers means thatthe unreacted monomer content is less than 1% by mass (typically lessthan 0.1% by mass) of the polymerization product (a). The polymerizationproduct (a) may comprise other materials (e.g. polymerization initiator,solvent, dispersion medium, etc.) besides the monomers used in thepolymerization to obtain the product.

[Embodiment in which Polymerization Product (a) is Partially-PolymerizedProduct]

In a preferable embodiment, the polymerization product (a) can be apartially-polymerized product resulting from partial polymerization ofthe monomer mixture. The term “partially-polymerized product” hereinrefers to a polymerization product in which its monomeric components arepartially polymerized. Such a partially-polymerized product is typicallyin a syrup-like state (in a viscous liquid state) where the polymerformed from part of the monomer mixture is present along with unreactedmonomers. Hereinafter, a partially-polymerized product in such a statemay be referred to as “polymer syrup” or simply “syrup.” Thepolymerization method used in partially polymerizing the monomer mixtureis not particularly limited. A suitable method can be selected and usedamong various polymerization methods as those described earlier. Forinstance, a photopolymerization method can be preferably used.

The monomer conversion of the monomer mixture in such apartially-polymerized product (typically polymer syrup) is notparticularly limited. For instance, the conversion (monomer conversion)can be 70% by mass or lower, or it is preferably 60% by mass or lower.From the standpoint of the ease of preparation and application of thePSA composition comprising the partially-polymerized product, themonomer conversion is usually suitably 50% by mass or lower, orpreferably 40% by mass or lower (e.g. 35% by mass or lower). The lowerlimit of the monomer conversion is not particularly limited, it istypically 1% by mass or higher. For instance, it can be 2% by mass orhigher. From the standpoint of the adhesive properties, etc., themonomer conversion is usually suitably 5% by mass or higher, preferably10% by mass or higher, more preferably 15% by mass or higher, yet morepreferably 20% by mass or higher, or particularly preferably 25% by massor higher.

Herein, the monomer conversion of a polymerization product is determinedby the next method.

(Measurement of Monomer Conversion)

From a polymerization product, a sample of approximately 0.5 g iscollected and precisely weighed (mass W_(p1)). Subsequently, the sampleis heated at 130° C. for two hours to evaporate off unreacted monomers.The sample remaining after the heating is precisely weighed (massW_(p2)). The monomer conversion is determined by substituting therespective values into the next equation:

Monomer conversion (%)=(W _(p2) /W _(p1))×100

When partially polymerizing the monomer mixture, the polymerizationmethod is not particularly limited. A suitable method can be selectedand used among various polymerization methods as those describedearlier. From the standpoint of the efficiency and convenience, as themethod for partially polymerizing the monomer mixture, aphotopolymerization method can be preferably used. According to aphotopolymerization, depending on the polymerization conditions such asirradiation dose (light quantity), etc., the monomer conversion of themonomer mixture can be easily controlled.

With respect to the PSA composition comprising, as the polymerizationproduct (a), a partially-polymerized product of the monomer mixture, itcan be formulated so as to form PSA when unreacted monomers (possiblyincluding a monomer other than the monomers from the monomer mixture) inthe composition are polymerized by a suitable means to cure. The methodfor polymerizing the PSA composition to allow its curing is notparticularly limited. For instance, it can be the same with or differentfrom the polymerization method used in the partial polymerization of themonomer mixture. The PSA composition in such an embodiment may be in aform where it comprises the polymer formed from part of the monomermixture in unreacted monomers (typically in a form where the polymer isdissolved in the unreacted monomers). Thus, it may be viscous enough toallow application at ordinary temperature without dilution with asolvent or dispersion medium. Accordingly, it is preferable as a PSAcomposition essentially free of a solvent (i.e. a solvent-free PSAcomposition). Such a solvent-free PSA composition can form a PSA layerwhen a suitable curing means (polymerization means) is applied, such aslight irradiation, radioactive ray irradiation, etc. Being essentiallyfree of organic solvents, the solvent-free PSA composition is preferablefrom the standpoint of the environmental hygiene. In addition, it isalso advantageous in view that it does not require drying equipment forthe PSA composition or organic solvent collecting equipment, or thatthese equipment can be minimized or simplified.

That a PSA composition is essentially free of organic solvents meansthat the PSA-forming content of the PSA composition is 95% by mass orhigher (typically 98% by mass or higher, or preferably 99% by mass orhigher). In other words, it means that the solvent content of the PSAcomposition is 5% by mass or lower (typically 2% by mass or lower,preferably 1% by mass or lower).

The PSA composition (typically a solvent-free PSA composition)comprising the partially-polymerized product as its polymerizationproduct (a) can be easily prepared, for instance, by mixing apolymerization product (a) obtained by partially polymerizing themonomer mixture by a suitable polymerization method with othercomponents (e.g. photopolymerization initiator, crosslinking agent,acrylic oligomer (b) described later, unreacted monomers, etc.) used asnecessary.

As the curing method (polymerization method) used in forming PSA fromthe PSA composition comprising a partially-polymerized product as itspolymerization product (a), a photopolymerization method can bepreferably used. With respect to a PSA composition comprising apolymerization product (a) prepared by a photopolymerization method, itis particularly preferable to employ photopolymerization as the curingmethod. A polymerization product (a) obtained by photopolymerizationalready contains a photopolymerization initiator. When the PSAcomposition comprising the polymerization product (a) is cured to formPSA, the photo-curing can be carried out without any additionalphotopolymerization initiator. Alternatively, the PSA composition may beobtained by adding a photopolymerization initiator as necessary to thepolymerization product (a) prepared by photopolymerization. Theadditional photopolymerization initiator may be the same as or differentfrom the photopolymerization initiator used in preparing thepolymerization product (a). If the PSA composition is prepared by amethod other than photopolymerization, a photopolymerization initiatorcan be added to make it light-curable. The light-curable PSA compositionis advantageous as it can readily form a thick PSA layer.

The amount of photopolymerization initiator used is not particularlylimited. For instance, an aforementioned general amount of use ofphotopolymerization initiator can be suitably applied. The amount ofphotopolymerization initiator used herein refers to the combined amountof the photopolymerization initiator used in the partial polymerizationto obtain the polymerization product (a) and any photopolymerizationinitiator added afterwards.

When the polymerization product (a) is a partially-polymerized product,the partially-polymerized product may have a weight average molecularweight (Mw) of, for instance, about 3×10⁴ to 500×10⁴. From thestandpoint of the adhesive properties of the PSA composition comprisingthe partially-polymerized product, the Mw of the partially-polymerizedproduct is preferably 5×10⁴ or higher, or more preferably 10×10⁴ orhigher (e.g. 20×10⁴ or higher). In a preferable embodiment of the artdisclosed herein, the Mw of the partially-polymerized product can be30×10⁴ or higher (more preferably 40×10⁴ or higher, even more preferably50×10⁴ or higher, e.g. 60×10⁴ or higher). According to such anembodiment, greater adhesive properties can be obtained. From thestandpoint of the ease of preparation and application of the PSAcomposition, etc., the Mw of the partially-polymerized product isusually preferably 200×10⁴ or lower, or more preferably 150×10⁴ orlower.

Herein, the Mw of the partially-polymerized product can be measured bygas permeation chromatography (GPC). More specifically, for instance,using trade name “HLC-8120GPC” (available from Tosoh Corporation) as theGPC measurement system, a sample of the partially-polymerized productcan be subjected to a measurement under the conditions below and it canbe determined as the value based on standard polystyrene (GPCMeasurement Conditions)

-   -   Sample concentration: about 2.0 g/L (tetrahydrofuran solution)    -   Sample injection volume: 20 μL    -   Columns: trade name “TSK gel, super AWM-H+super AW4000+super        AW2500” (available from Tosoh Corporation)    -   Column size: each 6.0 mm I.D.×150 mm    -   Eluent: tetrahydrofuran (THF)    -   Flow rate: 0.4 mL/min    -   Detector: differential refractometer (RI)    -   Column temperature (measurement temperature): 40° C.

Unreacted monomers possibly in the partially-polymerized product haveessentially no influence on the Mw value determined from the GPCmeasurement. Thus, the Mw value obtained by the GPC measurement with thesample of the partially-polymerized product can be thought as the Mw ofthe polymer in the partially-polymerized product.

The composition of the monomeric components of the polymerizationproduct (a) (i.e. the composition of the monomer mixture) can beselected so that when the product of complete polymerization of themonomeric components will have a Tg of −70° C. or higher, but −20° C. orlower. From the standpoint of the initial adhesion to adherend (e.g. anadherend formed of a low-polar material such as an olefinic rubbermaterial), the Tg is preferably −30° C. or lower, or more preferably−35° C. or lower (e.g. −40° C. or lower). From the standpoint of thecohesion of the PSA, the Tg is preferably −65° C. or higher (e.g. −60°C. or higher). In a preferable embodiment of the art disclosed herein,the Tg based on the composition of the monomeric components of thepolymerization product (a) can be, for instance, −60° C. to −35° C.(typically −60° C. to −40° C.).

The PSA composition comprising the partially-polymerized product of themonomer mixture as the polymerization product (a) may comprise a curingagent such as a crosslinking agent as necessary in addition to thepolymerization product (a) and the initiator (which can be an initiatorused for partial polymerization of the monomer mixture or an initiatoradded afterwards, or both of these) used as necessary. For the curingagent, solely one species or a combination of two or more species can beused.

(Polymerization Product (a) Comprising Polyfunctional Monomer)

Preferable examples of the curing agent include the polyfunctionalmonomers exemplified as the monomer B2. These polyfunctional monomerscan be thought as crosslinking agents as well. For the polyfunctionalmonomer, solely one species or a combination of two or more species canbe used. From the standpoint of the reactivity, etc., an acrylate-basedpolyfunctional monomer (i.e. a polyfunctional monomer having one, two ormore acryloyl groups per molecule) is usually more preferable.

As the monomer mixture to obtain the polymerization product (a), amonomer mixture having a composition essentially free of apolyfunctional monomer (i.e. a monomer mixture formed of a monomerhaving one polymerizable functional group per molecule) can bepreferably used. Herein, that a monomer mixture is essentially free of apolyfunctional monomer means that the polyfunctional monomer content inthe monomer mixture is 0.05% by mass or lower (typically 0.01% by massor lower). According to a monomer mixture having such a composition, thesolubility of the polymer in the polymerization product (a) to unreactedmonomers can be increased. It is also preferable because the viscosityof the polymerization product (a) (polymer syrup) can be for its monomerconversion. The PSA composition according to a preferable embodiment maycomprise, for instance, the polymerization product (a) being apartially-polymerized product of a monomer mixture essentially free of apolyfunctional monomer and a polyfunctional monomer added (afterwards)to the polymerization product (a).

Other preferable examples of the curing agent include crosslinkingagents. As the crosslinking agent, a crosslinking agent commonly knownor used in the acrylic PSA field can be used. Examples includeepoxy-based crosslinking agents, isocyanate-based crosslinking agents,silicone-based crosslinking agents, oxazoline-based crosslinking agents,aziridine-based crosslinking agents, silane-based crosslinking agents,alkyletherified melamine-based crosslinking agent, metal chelate-basedcrosslinking agent, and the like. Alternatively, the PSA composition maybe essentially free of such a crosslinking agent.

The PSA composition comprising the partially-polymerized product of themonomer mixture as the polymerization product (a) may comprise, asnecessary, a polymerization product (or the second polymerizationproduct, hereinafter) prepared separately from the polymerizationproduct (a). The second polymerization product may be apartially-polymerized product or completely-polymerized product formedfrom monomeric components corresponding to a portion of all monomericcomponents of the acrylic PSA layer, with the portion being differentfrom the monomeric components of the polymerization product (a). The PSAcomposition disclosed herein may comprise, as the second polymerizationproduct, for instance, a polymer having a lower Mw than the polymer inthe polymerization product (a) (preferably a polymer having acomposition whose monomeric components comprise an acrylic monomer at aratio higher than 50% by mass). The PSA composition having such acomposition may cure with irradiation of active energy rays (typicallyUV rays), etc., to form a PSA that provides excellent adhesion to alow-polar surface such as an olefinic rubber material surface.

In the PSA, the second polymerization product may serve as a tackifierto improve at least either its adhesion to adherend (e.g. an adherendformed of a low-polar material such as an olefinic rubber material) orthe cohesion of the PSA. When the PSA composition is cured by activeenergy ray irradiation (e.g. UV ray irradiation), the secondpolymerization product is preferably less likely to cause inhibition ofcuring (e.g. inhibition of polymerization of unreacted monomers in thePSA composition) as compared to tackifier resins (typically rosin-basedand terpene-based tackifiers, etc.) for use in general acrylic PSA.Thus, when the PSA composition disclosed herein is formulated as anactive energy ray-curable PSA composition, the amount of a generaltackifier resin based on such as rosin or terpene in the PSA compositionis preferably 0 to 10% by mass (more preferably 0 to 5% by mass, or evenmore preferably 0 to 2% by mass). Herein, a content of 0% by mass meansthat no tackifier resins are contained.

(Acrylic Oligomer (b))

The PSA composition according to a preferable embodiment may comprise,as the second polymerization product, an acrylic oligomer (b) having aMw of 2×10⁴ or lower (typically 0.1×10⁴ to 2×10⁴). The acrylic oligomer(b) is a polymer comprising an acrylic monomer (i.e. a monomer having atleast one (meth)acryloyl group per molecule) as its monomeric component.Accordingly, the acrylic oligomer (b) may comprise a monomer having atleast one methacryloyl group per molecule as part or the entirety of itsmonomeric components. The acrylic monomer content in the monomericcomponents of the acrylic oligomer (b) is typically greater than 50% bymass, preferably 60% by mass or greater, more preferably 70% by mass orgreater. In a preferable embodiment, the acrylic monomer content can be80% by mass or greater, or even 90% by mass or greater. The acrylicoligomer (b) may have a composition essentially consisting of an acrylicmonomer.

The composition of the monomeric components (i.e. the polymercomposition) of the acrylic oligomer (b) can be selected so that the Tgof the acrylic oligomer (b) is, but not limited to, 10° C. or higher,but 150° C. or lower. Herein, the Tg of the acrylic oligomer (b) refersto the value determined based on the composition of the monomericcomponents of the acrylic oligomer (b) in the same manner as the Tgbased on the composition of all monomeric components. From thestandpoint of the initial adhesion to an adherend surface (e.g. asurface formed of a low-polar material such as an olefinic rubbermaterial), the Tg of the acrylic oligomer (b) is preferably 120° C. orlower, or more preferably 100° C. or lower. From the standpoint of thecohesion of the PSA, the Tg of the acrylic oligomer (b) is preferably15° C. or higher, or more preferably 20° C. or higher (more preferably25° C. or higher). In a preferable embodiment of the art disclosedherein, the Tg of the acrylic oligomer (b) can be, for instance, 35° C.to 80° C.

The acrylic oligomer (b) can be prepared typically by polymerizing itsmonomeric components. The method or embodiment of the polymerization isnot particularly limited. Various heretofore known polymerizationmethods (e.g. solution polymerization, emulsion polymerization, bulkpolymerization, photopolymerization, radiation-induced polymerization,etc.) can be employed in suitable embodiments. The type and amount ofinitiator possibly used as necessary are generally as described above,and thus not repeated here.

From the standpoint of the adhesion to a low-polar surface such as anolefinic rubber material surface, the Mw of the acrylic oligomer (b) ispreferably 1.5×10⁴ or lower, more preferably 1×10⁴ or lower, or yet morepreferably 0.8×10⁴ or lower (e.g. 0.6×10⁴ or lower). From the standpointof the cohesion of the PSA, etc., the Mw of the acrylic oligomer (b) ispreferably 800 or higher, or more preferably 0.1×10⁴ or higher (e.g.0.2×10⁴ or higher). The Mw of the acrylic oligomer (b) can be measuredby GPC, similarly to the Mw of the polymer in the polymerization product(a).

To adjust the molecular weight of the acrylic oligomer (b), a chaintransfer agent can be used in the polymerization. Examples of the usablechain transfer agent include a compound having a mercapto group,thioglycolic acid and its derivatives, etc. Specific examples of themercapto group-containing compound include octylmercaptan, n-dodecylmercaptan, t-dodecyl mercaptan, etc. Specific examples of thethioglycolic acid and its derivatives include, besides thioglycolicacid, ethyl thioglycolate, propyl thioglycolate, butyl thioglycolate,t-butyl thioglycolate, 2-ethylhexyl thioglycolate, octyl thioglycolate,decyl thioglycolate, and dodecyl thioglycolate as well as thioglycolicacid esters such as thioglycolic acid ester of ethylene glycol,thioglycolic acid ester of neopentyl glycol, thioglycolic acid ester ofpentaerythritol, etc. Particularly preferable examples of the chaintransfer agent include thioglycolic acid and n-dodecyl mercaptan.

The amount of the chain transfer agent used is not particularly limited.It can be suitably adjusted in accordance with the Mw of the targetacrylic oligomer (b), etc. Usually, the chain transfer agent ispreferably used in an amount of about 0.1 to 20 parts by mass(preferably 0.2 to 15 parts by mass, more preferably 0.3 to 10 parts bymass) relative to 100 parts by mass of the monomeric components of theacrylic oligomer (b).

In the PSA composition comprising the polymerization product (a) andacrylic oligomer (b), the acrylic oligomer (b) content can be, forinstance, 1 part by mass or greater to 100 parts by mass of thepolymerization product (a), and it is usually suitably 3 parts by massor greater. From the standpoint of obtaining greater effects of theacrylic oligomer (b), the acrylic oligomer (b) content to 100 parts bymass of the polymerization product (a) is preferably 5 parts by mass orgreater, or more preferably 10 parts by mass or greater (e.g. 15 partsby mass or greater). From the standpoint of the curing properties of thePSA composition, the acrylic oligomer (b) content to 100 parts by massof the polymerization product (a) is suitably 150 parts by mass or less,or preferably 100 parts by mass or less (e.g. 70 parts by mass or less).From the standpoint of the adhesion to a low-polar surface such as anolefinic rubber material surface, etc., the acrylic oligomer (b) contentis more preferably 50 parts by mass or less, or yet more preferably 40parts by mass or less (e.g. 30 parts by mass or less).

(Monomer A Content)

The art disclosed herein can be preferably implemented in an embodimentwhere the PSA composition comprises the polymerization product (a) andacrylic oligomer (b), with one or each of these comprising an aminogroup-containing (meth)acrylate (monomer A) in its monomeric components.

In such a PSA composition comprising the polymerization product (a) andacrylic oligomer (b), when the polymerization product (a) comprises amonomer A as its monomeric component, the monomer A content can be, forinstance, 0.1% by mass or higher (typically 0.2% by mass or higher).From the standpoint of obtaining greater effects of the monomer A, themonomer A content is suitably higher than 0.2% by mass, preferably 0.5%by mass or higher, more preferably 0.7% by mass or higher, or yet morepreferably 1.0% by mass or higher (e.g. 1.2% by mass or higher). Fromthe standpoint of further increasing the adhesion to a low-polarmaterial such as an olefinic rubber material, the monomer A content canbe 1.5% by mass or higher (typically higher than 1.5% by mass), 2.0% bymass or higher, or even 3.0% by mass or higher. From the standpoint ofthe polymerization reactivity and initial adhesion, etc., the monomer Acontent in the monomeric components of the polymerization product (a) isusually suitably 25% by mass or lower, or it can be typically 20% bymass or lower, preferably 15% by mass or lower, more preferably 12% bymass or lower (e.g. 10% by mass or lower).

When the acrylic oligomer (b) comprises a monomer A in its monomericcomponents, the monomer A content is suitably 0.5% by mass or higher ofthe monomeric components, or preferably 1% by mass or higher (e.g. 2% bymass or higher, typically 3% by mass or higher). From the standpoint offurther increasing the adhesion to a surface of a low-polar materialsuch as an olefinic rubber material, it is preferably 10% by mass orhigher, more preferably 15% by mass or higher, or yet more preferably20% by mass or higher (e.g. 25% by mass or higher). The upper limit ofthe monomer A content in the monomeric components of the acrylicoligomer (b) is not particularly limited. For instance, the acrylicoligomer (b) can be a homopolymer of the monomer A. From the standpointof the polymerization reactivity and initial adhesion, etc., the monomerA content in the monomeric components of the acrylic oligomer (b) issuitably 90% by mass or lower and can be typically 80% by mass or lower,preferably 70% by mass or lower, or more preferably 65% by mass or lower(e.g. 60% by mass or lower).

In the PSA composition according to a preferable embodiment, each of thepolymerization product (a) and acrylic oligomer (b) comprises a monomerA in its monomeric components. In the PSA composition in such anembodiment, there are no particular limitations to the ratio(A_(O)/A_(S)) of mass A_(O) of monomer A included as a monomericcomponent of the acrylic oligomer (b) to mass As of monomer A includedas a monomeric component of the polymerization product (a). Forinstance, it can be about 0.1 to 25 (typically 0.2 to 20). From thestandpoint of the adhesion to a low-polar surface such as an olefinicrubber material surface, etc., the ratio (A_(O)/A_(S)) is suitably 0.5or higher, preferably 0.7 or higher, more preferably 1.0 or higher, oreven more preferably 1.2 or higher (e.g. 1.5 or higher). The ratio(A_(O)/A_(S)) is usually suitably 15 or lower. It can be, for instance,10 or lower (typically 7 or lower).

(Composition of Polymerization Product (a))

The art disclosed herein can be preferably implemented in an embodimentwhere the monomeric components of the polymerization product (a)comprises an acyclic alkyl (meth)acrylate as the monomer B1. Its contentcan be 30% by mass or more of the monomeric components of thepolymerization product (a), and it is usually suitably 40% by mass orgreater, preferably 50% by mass or greater, or more preferably 60% bymass or greater (typically greater than 60% by mass). When the monomer Ais included in the monomeric components of the polymerization product(a), the ratio of acyclic alkyl (meth)acrylate to monomeric componentsexcluding the monomer A can be preferably 50% by mass or greater, morepreferably 60% by mass or greater (e.g. 70% by mass or greater). Allother component(s) besides the monomer A can be acyclic alkyl(meth)acrylate(s). That is, the monomeric components of thepolymerization product (a) may have a composition consisting of anacrylic alkyl (meth)acrylate and a monomer A.

The art disclosed herein can be preferably implemented in an embodimentwhere the monomeric components of the polymerization product (a)comprises, as the monomer B1, a cycloalkyl (meth)acrylate. Such anembodiment may combine high levels of adhesion to a surface of alow-polar material such as an olefinic rubber material and cohesion ofthe PSA. The cycloalkyl (meth)acrylate content in the monomericcomponents of the polymerization product (a) can be, for instance, 1% bymass or greater, or it is usually suitably 3% by mass or greater,preferably 5% by mass or greater, or more preferably 10% by mass orgreater (e.g. 15% by mass or greater). From the standpoint of thepolymerization reactivity, its content is usually suitably less than 50%by mass, or can be preferably 40% by mass or less, more preferably 35%by mass or less (e.g. 30% by mass or less, typically 25% by mass orless).

In a preferable embodiment, the monomeric components of thepolymerization product (a) comprises an acyclic alkyl (meth)acrylate anda cycloalkyl (meth)acrylate. The mass ratio of acyclic alkyl(meth)acrylate to cycloalkyl (meth)acrylate (acyclic alkyl(meth)acrylate/cycloalkyl (meth)acrylate) can be, for instance, 1 to 20,or usually preferably 2 to 10, or more preferably 3 to 5.

When the monomeric components of the polymerization product (a)comprises a monomer A, the ratio of total amount of acyclic alkyl(meth)acrylate and cycloalkyl (meth)acrylate to monomeric componentsexcluding the monomer A is preferably 80% by mass or higher, morepreferably 85% by mass or higher, or yet more preferably 90% by mass orhigher (e.g. 95% by mass or higher). The art disclosed herein can bepreferably implemented in an embodiment where the monomeric componentsof the polymerization product (a) consist of an acyclic alkyl(meth)acrylate, a cycloalkyl (meth)acrylate and a monomer A.

Specific preferable examples of the monomeric components of thepolymerization product (a) include a composition comprising 2EHA, CHAand DMAEM; a composition comprising 2EHA, BA, CHA and DMAEM; acomposition comprising BA, CHA and DMAEM; a composition comprising 2EHA,CHA and DMAEA; a composition comprising 2EHA, BA, CHA and DMAEA; acomposition comprising BA, CHA and DMAEA; a composition comprising 2EHA,CHMA and DMAEM; a composition comprising 2EHA, BA, CHMA and DMAEM; acomposition comprising BA, CHMA and DMAEM; a composition comprising2EHA, CHMA and DMAEA; a composition comprising 2EHA, BA, CHMA and DMAEA;a composition comprising BA, CHMA and DMAEA; and the like. Inparticular, a composition comprising at least CHA is preferable.

(Composition of Acrylic Oligomer (b))

The art disclosed herein can be preferably implemented in an embodimentwhere the acrylic oligomer (b) comprises a cycloalkyl (meth)acrylate asthe monomer B1. From the standpoint of the adhesion to a surface of alow-polar material such as an olefinic rubber material and cohesion ofthe PSA, its content can be, for instance, 5% by mass or more of themonomeric components of the acrylic oligomer (b), or is usually suitably10% by mass or more, preferably 20% by mass or more, or more preferably30% by mass or more (e.g. 40% by mass or more).

When a monomer A is included in the monomeric components of the acrylicoligomer (b), the ratio of cycloalkyl (meth)acrylate to monomericcomponents excluding the monomer A is suitably 70% by mass or higher, orcan be preferably 80% by mass or higher, or more preferably 90% by massor higher (e.g. 95% by mass or higher, typically 97% by mass or higher).The art disclosed herein can be preferably implemented in an embodimentwhere the monomeric components of the acrylic oligomer (b) consist of acycloalkyl (meth)acrylate and a monomer A.

As the cyclohexyl (meth)acrylate, species such as CHA, CHMA, IBXA andIBXMA described earlier can be used. These can be used singly as onespecies or in a combination of two or more species.

Specific preferable examples of the acrylic oligomer (b) include acopolymer of CHMA and DMAEM, copolymer of CHMA, IBXMA and DMAEM;copolymer of CHMA, IBXA and DMAEM; copolymer of CHA and DMAEM; copolymerof CHA, IBXMA and DMAEM; copolymer of CHA, IBXA and DMAEM; copolymer ofCHMA and DMAEA; copolymer of CHMA, IBXMA and DMAEA; copolymer of CHMA,IBXA and DMAEA; copolymer of CHA and DMAEA; copolymer of CHA, IBXMA,DMAEA; copolymer of CHA, IBXA and DMAEA, etc. In particular, a copolymercomprising at least CHMA is preferable.

(Conditions of UV Irradiation)

In a preferable embodiment, the photopolymerization for forming a PSAfrom the PSA composition can be carried out by irradiation of UV rays.As the UV lamp used for the UV irradiation, a lamp having its spectraldistribution in a wavelength range of 300 nm to 400 nm can be preferablyused. For instance, a chemical lamp, a chemical lamp, black light (e.g.a black light available from Toshiba Lighting and TechnologyCorporation), metal halide lamp and the like can be used as the lightsource. In particular, it is preferable to irradiate UV rays so that theintensity at 300 nm to 400 nm is 1 mW/cm² to 50 mW/cm². The intensity ofUV rays being 50 mW/cm² or lower (typically 40 mW/cm² or lower, forinstance, 30 mW/cm² or lower) is advantageous from the standpoint ofobtaining greater adhesive properties. The intensity of UV rays being 1mW/cm² or higher (more preferably 2 mW/cm² or higher, for instance, 3mW/cm² or higher) is advantageous from the standpoint of theproductivity. The intensity of UV rays can be measured, using anindustrial UV checker (available from Topcon Corporation, trade name“UVR-T1” with light detector model number “UD-T36”) with peaksensitivity at 350 nm in wavelength.

[Embodiment where Polymerization Product (a) is Completely-PolymerizedProduct]

The art disclosed herein can be preferably practiced also in anembodiment where the polymerization product (a) is acompletely-polymerized product at a monomer conversion of greater than95% by mass (typically greater than 99% by mass). The PSA compositioncomprising such a polymerization product (a) is preferably essentiallyfree of unreacted monomers. For instance, the unreacted monomer contentis preferably less than 1% by mass, or more preferably less than 0.5% bymass. When the polymerization product (a) is a completely-polymerizedproduct, its Mw can be preferably 20×10⁴ or higher, more preferably30×10⁴ or higher, for instance, 40×10⁴ or higher. The upper Mw limit ofthe polymerization product (a) is not particularly limited. From thestandpoint of the ease of preparation and application of the PSAcomposition, etc., the Mw of the polymerization product (a) is usuallypreferably 200×10⁴ or lower, or more preferably 150×10⁴ or lower.

For example, such an embodiment can be preferably applied to a PSAcomposition whose adhesive components are diluted (dissolved ordispersed) to suitable viscosity with a solvent, such as in, forinstance, a solvent-based PSA composition, water-dispersed PSAcomposition (typically an emulsion-type PSA composition), etc. The PSAcomposition in such an embodiment can form a high performance PSA upon asimple curing treatment such as drying the PSA composition because itincludes the completely-polymerized product having a relatively highmolecular weight. In a preferable embodiment, the monomeric componentsof the polymerization product (a) may have essentially the samecomposition as that of all monomeric components in the acrylic PSAlayer.

A solvent-based PSA composition can be easily prepared by, for instance,subjecting a monomer mixture having a composition corresponding to themonomeric components of the polymerization product (a) to solutionpolymerization. As the polymerization solvent, organic solvents commonlyknown or used in solution polymerization of an acrylic monomer can beused, such as ethyl acetate, toluene, hexane, a solvent mixture ofthese, etc. The embodiment of solution polymerization is notparticularly limited and a heretofore known embodiment can be suitablyapplied. The type and amount of initiator that can be used as necessaryare generally as described above. Thus, they are not repeated here. Thesolvent-based PSA composition can be prepared by dissolving apolymerization product obtained by a polymerization method other thansolution polymerization into a suitable organic solvent. From thestandpoint of the productivity, etc., it is preferably prepared bysolution polymerization.

An emulsion-type PSA composition can be easily prepared by, forinstance, subjecting a monomer mixture having a compositioncorresponding to the monomeric components of the polymerization product(a) to emulsion polymerization. The embodiment of emulsionpolymerization is not particularly limited and a heretofore knownembodiment can be suitably applied. The type and amount of initiatorthat can be used as necessary are generally as described above. Thus,they are not repeated here. Alternatively, the emulsion-type PSAcomposition can be prepared by emulsifying a polymerization productobtained by a polymerization method other than emulsion polymerizationinto an aqueous solvent (typically water). From the standpoint of theproductivity, etc., it is preferably prepared by emulsionpolymerization.

In addition to the polymerization product (a), the PSA composition(typically a solvent-based or water-dispersed PSA composition) cancomprise, as necessary, a crosslinking agent as those described earlier.For the crosslinking agent, solely one species or a combination of twoor more species can be used. Examples of a particularly preferablecrosslinking agent include an isocyanate-based crosslinking agent andepoxy-based crosslinking agent.

As the isocyanate-based crosslinking agent, various polyfunctionalisocyanate compounds can be used. Specific examples include loweraliphatic polyisocyanates such as 1,2-ethylene diisocyanate,1,4-butylene diisocyanate, 1, 6-hexamethylene diisocyanate, etc.;alicyclic polyisocyanates such as cyclopentylene diisocyanate,cyclohexylene diisocyanate, isophorone diisocyanate, hydrogenatedtolylene diisocyanate, hydrogenated xylene diisocyanate, etc.; aromaticpolyisocyanates such as 2,4-tolylene diisocyanate, 2,6-tolylenediisocyanate, 4,4′-diphenylmethane diisocyanate, xylylene diisocyanate,etc.; and the like. Among these, solely one species or a combination oftwo or more species can be used.

Examples of a commercial product that can be used as theisocyanate-based crosslinking agent include an adduct oftrimethylolpropane and tolylene diisocyanate (trade name “CORONATE L”available from Nippon Polyurethane Industry Co., Ltd.), an adduct oftrimethylolpropane and hexamethylene diisocyanate (trade name “CORONATEHL” available from Nippon Polyurethane Industry Co., Ltd.), anisocyanurate of hexamethylene diisocyanate (available from NipponPolyurethane Industry, Co., Ltd.; trade name “CORONATE HX”), and anadduct of trimethylolpropane and xylylene diisocyanate (trade name“TAKENATE D-110N” available from Mitsui Chemicals, Inc.).

As the epoxy-based crosslinking agent, various polyfunctional epoxycompounds can be used. Specific examples includeN,N,N′,N′-tetraglycidyl-m-xylenediamine, diglycidylaniline,1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidylether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidylether, propylene glycol diglycidyl ether, polyethylene glycol diglycidylethers, polypropylene glycol diglycidyl ethers, sorbitol polyglycidylethers, glycerol polyglycidyl ethers, pentaerythritol polyglycidylethers, polyglycerol polyglycidyl ethers, sorbitan polyglycidyl ethers,trimethylolpropane polyglycidyl ethers, diglycidyl adipate, o-diglycidylphthalate, triglycidyl tris(2-hydroxyethyl)isocyanurate, resorcinoldiglycidyl ether and bisphenol-S diglycidyl ether; as well asepoxy-based resins having two or more epoxy groups per molecule. Thesecan be used singly as one species or in a combination of two or morespecies.

As the epoxy-based crosslinking agent, a commercial product can be usedas well, such as trade name “TETRAD C”(1,3-bis(N,N-diglycidylaminomethyl)cyclohexane) available fromMitsubishi Gas Chemical Company, Inc., trade name “TETRAD X”(N,N,N′,N′-tetraglycidyl-m-xylenediamine) from the same company and thelike.

The amount of crosslinking agent is usually suitably about 0.01 to 15parts by mass relative to 100 parts by mass of all monomeric componentsin the acrylic PSA layer and preferably about 0.1 to 10 parts by mass(e.g. about 0.2 to 2 parts by mass). The PSA composition comprising acrosslinking agent used in such an amount is preferable because it islikely to form a PSA with well-balanced adhesion to a low-polar materialsuch as an olefinic rubber material and cohesion.

The PSA composition (typically a solvent-based or water-dispersed PSAcomposition) can comprise a tackifier as necessary. As the tackifier, atackifier resin commonly known or used in the acrylic PSA field can beused, such as rosin-based, terpene-based, hydrocarbon-based,epoxy-based, polyamide-based, phenol-based, ketone-based species, etc.These tackifier resins can be used singly as one species or in acombination of two or more species. The amount of the tackifier resinused is not particularly limited. In view of the balance betweenadhesion to a low-polar material such as an olefinic rubber material andcohesion of the PSA, to 100 parts by mass of all monomeric components inthe acrylic PSA layer, it is usually suitably about 10 to 100 parts bymass (more preferably 15 to 80 parts by mass, or yet more preferably 20to 60 parts by mass).

As the tackifier, the acrylic oligomer (b) described above may be used,or a tackifier resin as described above and the acrylic oligomer (b) canbe used together.

<Additives>

The PSA composition in the art disclosed herein may further comprise, asnecessary, known additives that can be used in acrylic PSA, such asplasticizer, softener, filler, colorant (pigment, dye, etc.),antioxidant, leveling agent, stabilizer, preservative, etc., as far asthe effects of the present invention are not significantly hindered.

For instance, when the PSA composition is cured by photopolymerizationto form a PSA layer, to color the PSA layer, a pigment (coloringpigment) can be used as a colorant in an amount that does not hinder thephotopolymerization. When the color of the PSA layer is desirably black,for instance, carbon black can be preferably used as the colorant. Inview of the extent of coloring, photopolymerization reactivity, etc.,the amount of carbon black used is desirably selected from a range of,for instance, 0.15 part by mass or less (e.g. 0.001 to 0.15 part bymass), or preferably 0.01 to 0.1 part by mass.

<Gel Fraction of PSA>

In the acrylic PSA layer included in a PSA sheet disclosed herein, thePSA constituting the PSA layer preferably has a gel fraction of, forinstance, about 10% by mass or higher. To obtain such a gel fraction,suitable conditions can be selected with respect to the composition ofthe monomeric components of the PSA composition used for forming the PSAlayer, conversion of the monomeric components, Mw of the polymer in thePSA composition, whether or not to use a polyfunctional monomer and itsamount used if any, whether or not to use a crosslinking agent and itsamount used if any, conditions for forming the PSA layer (curingconditions for the PSA composition, such as light irradiation conditionsand drying conditions) and so on. From the standpoint of the cohesion,the gel fraction is suitably 15% or higher, preferably 20% or higher, ormore preferably 25% or higher (e.g. 30% or higher). From the standpointof the adhesion (e.g. adhesion to a low-polar material such as anolefinic rubber material), the gel fraction is suitably 90% or lower,preferably 85% or lower, or more preferably 80% or lower (e.g. 75% orlower). In a preferable embodiment, the gel fraction can be 70% orlower, preferably 60% or lower, or more preferably 50% or lower (yetmore preferably 45% or lower, for instance, 40% or lower).

The gel fraction can be measured by the following method: In particular,a measurement sample weighing approximately 0.1 g is wrapped into apouch with a porous tetrafluoroethylene resin sheet of 0.2 μm averagepore diameter, and the opening is tied with twine. The mass of thewrapping (the combined mass of the porous tetrafluoroethylene resinsheet and the twine) Wa (mg) is measured in advance. The mass of thepouch (the combined mass of the PSA and the wrapping) Wb (mg) ismeasured. The pouch is placed in a screw vial of volume 50 mL (one screwvial used for each pouch), and the screw vial is filled with ethylacetate. This is set still at room temperature (typically at 23° C.) forseven days, and the pouch is then removed and allowed to dry at 120° C.for two hours. The mass We (mg) of the pouch after dried is measured.The gel fraction of the PSA can be determined by substituting the Wa, Wband We into the following:

Gel fraction (%)=(Wc−Wa)/(Wb−Wa)×100

As the porous tetrafluoroethylene resin sheet, can be used trade name“NITOFLON® NTF1122” (0.2 μm average pore diameter, 75% porosity, 85 μmthick) available from Nitto Denko Corporation or an equivalent productcan be used.

<Filler>

The PSA sheet disclosed herein may comprise a PSA layer comprising somefiller. The inclusion of filler in a PSA layer may increase the cohesionof the PSA layer. The use of filler allows adjustment of the 10%compression hardness and breaking strength of the PSA sheet describedlater. The filler-containing PSA layer can be a PSA layer constitutingan adhesive face or a PSA layer not constituting an adhesive face. Thefiller-containing PSA layer can be a bubble-containing layer or abubble-free layer.

As the filler, various particulate substances can be used. Examples of amaterial constituting such a particulate substance include metals suchas copper, nickel, aluminum, chromium, iron, stainless steel, etc.;metal oxides such as alumina, zirconia, etc.; carbides such as siliconcarbide, boron carbide, nitrogen carbide, etc.; nitrides such asaluminum nitride, silicon nitride, boron nitride, etc.; inorganicmaterials such as calcium carbide, calcium carbonate, aluminumhydroxide, glass, silica, etc.; polymers such as a polystyrene, acrylicresin (e.g. poly(methyl methacrylate)), phenol resin, benzoguanamineresin, urea resin, silicone resin, nylon, polyester, polyurethane,polyethylene, polypropylene, polyamide, polyimide, silicone, vinylidenechloride, etc.; and the like. Alternatively, particles of naturalmaterials such as volcanic shirasu, sand and the like can be used. Theexternal form of such a particulate substance is not particularlylimited, and can be, for instance, globular, flaky, irregularly-shaped,etc. The particle structure of the particulate substance is notparticularly limited. For instance, it may have a dense structure, aporous structure, a hollow structure, etc.

In a preferable embodiment, as the filler, a particulate substancehaving a hollow structure, that is, hollow particles, can be used. Whenthe PSA layer comprising hollow particles is formed from a PSAcomposition that is light-curing (e.g. UV-curing), from the standpointof the light curability (polymerization reactivity) of the PSAcomposition, it is preferable to use hollow particles formed from aninorganic material. Examples of such hollow particles include balloonsmade of glass such as hollow glass balloons, etc.; hollow balloons madeof metal compounds such as hollow alumina balloons, etc.; hollowballoons made of ceramics such as hollow ceramic balloons, etc.; and thelike.

As the hollow glass balloon, can be used commercial products such astrade names “GLASS MICRO BALLOON” available from Fuji Silysia ChemicalLtd.; trade names “CEL-STAR Z-20,” “CEL-STAR Z-27,” “CEL-STAR CZ-31T,”“CEL-STAR Z-36,” “CEL-STAR Z-39,” “CEL-STAR T-36” and “CEL-STAR PZ-6000”available from Tokai Kogyo Co. Ltd.; trade names “SEILAX FINE BALLOON”available from Fine Balloon KK; trade names “G-CEL® 5020,” “G-CEL®7014,” “SPHERICEL® 110P8,” “SPHERICEL® 25P45,” “SPHERICEL® 34P30” and“SPHERICEL® 60P18” available from Potters-Ballotini Co., Ltd.; tradenames “SUPER BALLOON BA-15” and “SUPER BALLOON 732C” available fromShowa Chemical Industry Co., Ltd.; and the like.

The average particle diameter of the hollow particles used is notparticularly limited. For example, it can be selected from a range of 1μm to 500 μm, preferably 5 μm to 400 μm, more preferably 10 μm to 300μm, or yet more preferably 10 μm to 200 μm (e.g. 10 μm to 150 μm). Theaverage particle diameter of the hollow particles is usually suitably atmost 50% of the thickness of the layer containing the hollow particles,or preferably at most 30% (e.g. at most 10 V.

The specific gravity of the hollow particles is not particularlylimited. In view of the uniform dispersibility in the PSA composition,mechanical strength, UV permeability, etc., for instance, it can beselected from a range of 0.1 g/cm³ to 1.8 g/cm³, preferably 0.1 g/cm³ to1.5 g/cm³, or more preferably 0.1 g/cm³ to 0.5 g/cm³ (e.g. 0.2 g/cm³ to0.5 g/cm³). The amount of the hollow particles used is not particularlylimited. For instance, it can be about 10 to 50% by volume of the volumeof the PSA layer comprising the hollow particles.

In a PSA sheet comprising a non-adhesive layer, such filler (e.g. hollowparticles) may be included in the non-adhesive layer. The type ofpreferable filler in a non-adhesive layer and its structure, averageparticle diameter, specific gravity, etc., can be the same as when thefiller is included in an adhesive layer. Each of an adhesive layer and anon-adhesive layer may comprise filler.

The PSA sheet disclosed herein can be preferably made in an embodimentwhere a bubble-containing layer that does not constitute an adhesiveface such as the intermediate layer 223 in FIG. 4 comprises filler whilea bubble-free layer that constitutes an adhesive face such as the firstand second adhesive layers 221 and 222 in FIG. 4 are free of filler. ThePSA sheet having such constitution may combine adhesion and cohesion ata high level.

<Thickness of PSA Sheet>

In the PSA sheet disclosed herein, the acrylic PSA layer constitutingthe adhesive face has a thickness of, for instance, 1 μm or larger. Fromthe standpoint of the adhesiveness, it has a thickness of suitably 5 μmor larger, preferably 10 μm or larger, or more preferably 20 μm orlarger (e.g. 30 μm or larger, typically 35 μm or larger). In apreferable embodiment, the thickness of the acrylic PSA layerconstituting the adhesive face can be 40 μm or larger (typically 50 μmor larger). The thickness of the acrylic PSA layer constituting theadhesive face can be 70 μm or larger (e.g. 90 μm or larger) as well. Forinstance, in a PSA sheet having the first adhesive face formed with anacrylic PSA layer and the second adhesive face formed with another PSAlayer, these thickness ranges can also be preferably applied to the PSAlayer forming the second adhesive face.

In the PSA sheet in an embodiment comprising, in addition to an acrylicPSA layer constituting an adhesive face, another PSA layer notconstituting an adhesive face—that is, a PSA layer not exposed to thesurface of the PSA sheet, the lower limit of the thickness of the otherPSA layer is not particularly limited. For instance, it can be 0.05 μmor larger (typically 0.1 μm or larger).

The upper limit of the thickness of the PSA layer constituting theadhesive face is not particularly limited. The preferable upper limit ofthe thickness may also vary depending on the constitution of the entirePSA sheet including the PSA layer, etc.

For instance, when the acrylic PSA layer is a bubble-free adhesivelayer, its thickness can be, for example, about 1000 μm or smaller. Fromthe standpoint of the cohesion, etc., usually, the thickness is suitably700 μm or smaller, or preferably 600 μm or smaller (e.g. smaller than500 μm). In a preferable embodiment, the thickness can be 250 μm orsmaller (more preferably 200 μm or smaller, typically 120 μm or smaller,e.g. 70 μm or smaller). These thickness ranges can be preferably appliedto a bubble-free adhesive layer not constituting an adhesive face and anon-acrylic bubble-free adhesive layer constituting an adhesive face.

When the acrylic PSA layer constituting an adhesive face is abubble-containing adhesive layer, its thickness can be, for instance,about 10 mm or smaller. From the standpoint of the ease of formation(e.g. light-curing properties of the PSA layer, the thickness is usuallysuitably 5 mm or smaller, or preferably 2 mm or smaller (e.g. 1 mm orsmaller). The thickness ranges can be preferably applied to abubble-containing adhesive layer not constituting an adhesive face or anon-acrylic bubble-containing adhesive layer constituting an adhesiveface.

When the PSA sheet disclosed herein comprises a bubble-free non-adhesivelayer (e.g. a plastic film), its thickness is not particularly limited.It can be, for instance, 0.001 μm or larger (typically 0.01 μm orlarger, e.g. 0.1 μm or larger). The upper limit of the thickness of thebubble-free non-adhesive layer is not particularly limited. From thestandpoint of the flexibility of the PSA sheet, etc., it is usuallysuitably smaller than 500 μm, preferably smaller than 250 μm, or morepreferably smaller than 200 μm (e.g. smaller than 100 μm).

When the PSA sheet disclosed herein comprises a bubble-containingnon-adhesive layer (e.g. a polyolefinic foam sheet such as apolyethylene-based foam sheet), its thickness is not particularlylimited. In a preferable embodiment, the bubble-containing non-adhesivelayer has a thickness of 10 μm or larger, but about 10 mm or smaller(more preferably 20 μm or larger, but smaller than 5 mm, typically 50 μmor larger, but smaller than 2 mm, for instance, 100 μm or larger, butsmaller than 1 mm).

The overall thickness (not including the thickness of any release liner)of the PSA sheet disclosed herein is not particularly limited. Thepreferable overall thickness of the PSA layer may also vary depending onthe construction, purpose of use and form of use of the PSA sheet, etc.

Herein, the overall thickness of a PSA sheet refers to the thicknessfrom the first adhesive face 21A through the second adhesive face 22A ina double-faced PSA sheet as shown in FIG. 2; and it refers to thethickness from the first adhesive face 21A through the back face (secondsurface 31A) in a substrate-supported single-faced PSA sheet as shown inFIG. 3. In other words, the overall thickness of a PSA sheet herein doesnot include the thickness of any release liner.

When the PSA sheet is free of a bubble-containing layer, the sheetusually has a thickness of suitably 5 μm or larger, and from thestandpoint of the adhesion, preferably 10 μm or larger, or morepreferably 20 μm or larger (e.g. 30 μm or larger, typically 35 μm orlarger). From the standpoint of the adhesion to EPDM and other olefinicrubber materials, the sheet thickness is preferably 50 μm or larger,more preferably 70 μm or larger, or yet more preferably 80 μm or larger(e.g. 90 μm or larger). The thickness of the PSA sheet can be, forinstance, about 1000 μm or smaller. From the standpoint of the cohesion,etc., it is suitably 800 μm or smaller, or preferably 700 μm or smaller(e.g. smaller than 600 μm). In a preferable embodiment, the thicknesscan be 300 μm or smaller (more preferably 250 μm or smaller, typically150 μm or smaller, e.g. 100 μm or smaller).

When the PSA sheet comprises a bubble-containing layer, its thicknesscan be, for instance, 10 μm or larger, or it is usually preferably 50 μmor larger (typically 100 μm or larger). From the standpoint of thecushioning properties, the thickness of the PSA sheet is suitably 300 μmor larger, preferably 500 μm or larger, or more preferably 700 μm orlarger (e.g. 1000 μm or larger). The thickness of the PSA sheet can be,for instance, about 15 mm or smaller, or it is usually suitably about 10mm or smaller, preferably 7 mm or smaller, or more preferably 5 mm orsmaller (e.g. 3 mm or smaller).

In the PSA sheet comprising a bubble-containing layer and a bubble-freelayer, the ratio of the thickness of the bubble-containing layer in theoverall thickness of the PSA sheet is not particularly limited and canbe, for instance, 10% or higher. From the standpoint of the cushioningproperties and flexibility of the PSA sheet, the ratio of thebubble-containing layer is preferably 25% or higher, more preferably 50%or higher, or even more preferably 70% or higher. From the standpoint ofobtaining yet greater cushioning properties, etc., the ratio of thethickness of the bubble-containing layer in the overall thickness of thePSA sheet can be 80% or higher, 85% or higher, or even 90% or higher.For instance, as shown in FIG. 5, the art disclosed herein can also bepreferably implemented in an embodiment where the PSA sheet is formedsolely of a bubble-containing adhesive layer. In this case, the ratio ofthe thickness of the bubble-containing layer in the overall thickness ofthe PSA sheet is 100%.

For instance, as shown in FIG. 4, in a PSA sheet 20 constituted withadhesive face-constituting PSA layers 221 and 222 backed with anintermediate layer 223, the ratios of the thicknesses of adhesiveface-constituting PSA layers 221 and 222 in the overall thickness of thePSA sheet can be individually, for instance, 0.1% or higher. From thestandpoint of the adhesion, etc., the ratios of their thicknesses areusually suitably 0.5% or higher, preferably 1% or higher, morepreferably 2% or higher, or yet more preferably 3% or higher.

When the PSA sheet disclosed herein comprises a bubble-free non-adhesivelayer (e.g. a plastic film), the ratio of the thickness of thebubble-free non-adhesive layer in the overall thickness of the PSA sheetis not particularly limited, but it is usually suitably 20% or lower.From the standpoint of obtaining greater conformability, the ratio ofthe thickness of the bubble-free non-adhesive layer is preferably 10% orlower, or more preferably 5% or lower.

<Properties of PSA Sheet> [Compression Hardness]

When the PSA sheet disclosed herein comprises a bubble-containing layer,its 10% compression hardness is preferably, but not particularly limitedto, 0.2 Pa or less. Herein the 10% compression hardness of a PSA sheetrefers to the load applied when at a measurement temperature of 25° C.,the PSA sheet is placed between plates and compressed to 90% of itsinitial thickness (100%). When the overall thickness of the PSA sheet isless than 25 mm, a minimal number of layers of the PSA sheet areoverlaid to at least 25 mm and the resulting laminate is placed betweenthe plates and measured for 10% compression hardness.

With the 10% compression hardness being 0.2 Pa or less, theconformability of the PSA sheet to the surface structure of adherend orits deformation will increase, allowing tighter adhesion of the PSAsheet to the adherend surface. From the standpoint of obtaining greaterconformability, the 10% compression hardness of the PSA sheet can be,for instance, 0.1 Pa or less, and is preferably 0.07 Pa or less, or morepreferably 0.05 Pa or less. From the standpoint of the handlingproperties of the PSA sheet, the 10% compression hardness is suitably0.007 Pa or greater, preferably 0.01 Pa or greater, or more preferably0.02 Pa or greater.

The 10% compression hardness of a PSA sheet can be measured based on JISK 6767. The 10% compression hardness of the PSA sheet can be controlledthrough the type (composition, bubble content, thickness, etc.) ofbubble-containing layer, presence or absence of a bubble-free layer,ratio of thickness of bubble-containing layer to overall PSA sheetthickness, use or absence of filler, and so on.

[Breaking Strength]

When the PSA sheet disclosed herein comprises a bubble-containing layer,its breaking strength is preferably, but not particularly limited to, 5Pa or less. The breaking strength of a PSA sheet herein refers to theload at break when a 10 mm wide strip as a test piece is cut out alongthe length direction (MD) of the PSA sheet, and at a measurementtemperature of 25° C., the test piece is stretched in the MD directionat a tensile speed of 300 mm/min at a chuck distance of 50 mm based onJIS K7161. With the breaking strength being 5 Pa or less, theconformability of the PSA sheet to the surface structure of adherend orits deformation will increase, allowing tighter adhesion of the PSAsheet to the adherend surface. From the standpoint of obtaining greaterconformability, the breaking strength of the PSA sheet is preferably 3Pa or less, or more preferably 2.5 Pa or less (e.g. 2 Pa or less). Fromthe standpoint of the handling properties and cohesion of the PSA sheet,etc., the breaking strength is suitably 0.1 Pa or greater, or preferably0.3 Pa or greater (e.g. 0.5 Pa or greater). The breaking strength of thePSA sheet can be controlled through the type (composition, bubblecontent, thickness, etc.) of bubble-containing layer, presence orabsence of a bubble-free layer, ratio of thickness of bubble-containinglayer to overall PSA sheet thickness, use or absence of filler, and soon.

[Cohesion]

The PSA sheet disclosed herein preferably exhibits a level of cohesionthat provides a holding time of 15 minutes or longer before its samplefalls off in the following holding power test.

(Holding Power Test)

A 20 mm wide strip prepared from a PSA sheet to be measured is used asthe measurement sample. When the PSA sheet to be measured is in a formof double-faced PSA sheet, 50 μm thick polyethylene terephthalate (PET)film should be applied to back one adhesive face in advance.

To a stainless steel (SUS) plate as the adherend, the sample ispress-bonded at its one end over a 20 mm wide by 20 mm long bonding areawith a 5 kg roller rolled once in one direction. The resultant is storedin the standard environment for 24 hours. Subsequently, based on JISZ0237(2004), the SUS plate is vertically suspended in an environment at40° C. and a 500 g load is applied to the free end of the sample. Withthe load being applied, it is stored in the environment at 40° C. andthe time taken for the sample to peel from the SUS plate and fall off ismeasured.

The measurement was taken with two or more measurement samples for eachPSA sheet and their arithmetic average value is used as its holdingtime.

A PSA sheet having a holding time of 15 minutes or longer according tothe holding power test is preferable, for instance, when used in a formof double-faced PSA sheet for applications for joining various types ofadherend to desirable locations. From the standpoint of the reliabilityof the joint, the holding time is preferably 20 minutes or longer, ormore preferably 30 minutes or longer.

<Adherend>

The PSA sheet disclosed herein has an adhesive face that providesexcellent adhesion to EPDM. Accordingly, it may exhibit great adhesionto surfaces formed of various materials including surfaces of EPDM andother olefinic rubbers as well as surfaces of other low-polar materials.The adherend material to which the adhesive face is applied is notparticularly limited. The adherend may have a surface formed of, forinstance, metallic materials such as stainless steel (SUS), aluminum,zinc-plated steel plate, etc.; inorganic materials such as glass,ceramic, etc.; resin materials such as polyolefinic resins includingpolycarbonate, polymethyl methacrylate (PMMA), polyethylene andpolypropylene as well as acrylonitrile-butadiene-styrene copolymer(ABS), polystyrene, polyethylene terephthalate (PET), etc.; olefinicrubber materials such as EPDM and thermoplastic olefinic elastomer;non-olefinic rubber materials such as natural rubber, acrylic rubber,styrene-based thermoplastic elastomer, etc.; a composite material ofthese; or the like. It can be applied to a surface painted with anacrylic, polyester-based, alkyd-based, melamine-based, urethane-based,acid-epoxy crosslinking-based, their composite-based (e.g. acrylicmelamine-based, alkyd melamine-based) paint or the like.

The PSA sheet disclosed herein can be preferably used in an embodimentwhere the adhesive face formed with the acrylic PSA layer (e.g. a PSAlayer (A)) is applied to a surface formed of an olefinic rubbermaterial, non-olefinic rubber material or polyolefinic resin. Examplesof the polyolefinic resin include polyethylene such as LDPE, LLDPE,HDPE, metallocene catalyst-based LDPE, polypropylene, ethylene-propylenecopolymer, ethylene-vinyl acetate copolymer, etc.

A particularly preferable embodiment of the use of the PSA sheetdisclosed herein is an embodiment where the adhesive face formed withthe acrylic PSA layer (e.g. a PSA layer (A)) is applied to a surfaceformed of an olefinic rubber material (or an olefinic rubber surface,hereinafter). The adhesive face is highly adhesive to the standard EPDMplate. Thus, it may exhibit excellent adhesion to EPDM and otherolefinic rubber materials.

A preferable embodiment of the use of the PSA sheet that comprises abubble-containing layer and has an adhesive face formed with a PSA layer(A) is an embodiment where the adhesive face is applied to a surfaceformed of an olefinic rubber material, non-olefinic rubber material orpolyolefinic resin. The adhesive face formed with the PSA layer (A) mayhave a high affinity to a low-polar surface because of the effects ofthe monomer A. Such effects of the monomer A in combination with thetight adhesion (great conformability to a surface structure anddeformation of adherend) due to the inclusion of the bubble-containinglayer in the PSA sheet can bring about excellent adhesion to surfaces oflow-polar materials such as olefinic rubber materials and polyolefinicresins. In addition, since it can conform well to deformation of theadherend because of the high conformability, it may also exhibitexcellent adhesion to an adherend formed of a material susceptible toelastic deformation, such as an olefinic rubber material and otherrubber materials.

A particularly preferable embodiment of the use of the PSA sheet thatcomprises a bubble-containing layer and has an adhesive face formed witha PSA layer (A) is an embodiment where the adhesive face formed as asurface of the PSA layer (A) is applied to an olefinic rubber surface.Because of the monomer As effects, the adhesive face has a high affinityto an olefinic rubber surface (e.g. a surface formed of EPDM). Suchmonomer As effects in combination with the high conformability to asurface structure and deformation of an olefinic rubber material due tothe inclusion of the bubble-containing layer in the PSA sheet can bringabout excellent adhesion to the olefinic rubber material.

Herein, the olefinic rubber material refers to a material comprising anolefinic rubber (typically a material whose olefinic rubber contentexceeds 50% by mass or the material). Specific examples include olefinicrubbers such as ethylene-propylene rubber (EPM),ethylene-propylene-diene rubber (EPDM) and butyl rubber (IIR) as well asvarious resin material comprising such olefinic rubbers. The olefinicrubber-containing resin material can be a resin material as a blend of athermoplastic resin (e.g. a polyolefin such as polypropylene) and anolefinic rubber. Typical examples of such a resin material include athermoplastic olefinic elastomer (TPO) that comprises the thermoplasticresin as its hard segment and the olefinic rubber as its soft segment.

Besides the olefinic rubber, the olefinic rubber material may comprise,as necessary, known additives that can be used in molded rubber parts,such as carbon black, colorant, plasticizer, filler, vulcanizing agent,vulcanization accelerator, foaming agent, and so on.

As the plasticizer, for instance, paraffin oils, waxes, naphthenics,aromatics, asphalts, drying oils (e.g. linseed oil), animal andvegetable oils, low molecular weight polymers, phthalic acid esters,phosphoric acid esters, alkyl sulfonic acid esters, etc., can be used.

As the filler, for instance, carbon black, zinc oxide, calciumcarbonate, magnesium carbonate, silicic acid or a salt thereof, talk,mica, bentonite, silica, alumina, aluminum silicate, acetylene black,aluminum powder, etc., can be used.

As the vulcanizing agent, for instance, sulfur, sulfur compounds,selenium, magnesium oxide, lead monoxide, zinc oxide, organic peroxides,polyamines, oximes (e.g. p-quinone dioxime, p,p′-dibenzoylquinonedioxime), nitroso compounds (e.g. p-dinitrosobenzine), resins (e.g.alkylphenol-formaldehyde resin, melamine-formaldehyde condensate),ammonium salts (e.g. ammonium benzoate), etc., can be used.

As the vulcanizsation accelerator, for instance, dithiocarbamic acids(e.g. sodium dimethyldithiocarbamate, sodium diethyldithiocarbamate,zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, etc.),thiazoles (e.g. 2-mercaptobenzothiazole, dibenzothiazyl disulfide,etc.), guanidines (e.g. diphenylguanidine, di-o-tolylguanidine, etc.),sulfenamides (e.g. benzothiazyl-2-diethylsulfenamide,N-cyclohexyl-2-benzothiazyl sulfenamide, etc.), thiurams (e.g.tetramethylthiuram monosulfide, tetramethylthiuram disulfide, etc.),xanthogenic acids (e.g. sodium isopropylxanthogenate, zincisopropylxanthogenate, etc.), aldehyde ammonias (e.g. acetaldehydeammonia, hexamethylenetetramine, etc.), aldehyde amines (e.g.n-butylaldehyde aniline, butylaldehyde monobutylamine, etc.) andthioureas (e.g. diethyl thiourea, trimethyl thiourea, etc.) can be used.

An example of a preferable object of application (object of adhesion) ofthe PSA sheet disclosed herein is an olefinic rubber material having acomposition in which an olefinic rubber (e.g. EPDM) is mixed with eithercarbon black or paraffin oil or with the both of these. When the acrylicPSA layer constituting the adhesive face is a PSA layer (A), accordingto an embodiment where it is applied to such an olefinic rubbermaterial, greater effects can be produced by the PSA layer (A)comprising the monomer A in its monomeric components.

<PSA Sheet-Bearing Part>

When the PSA sheet disclosed herein is used in an embodiment where theadhesive face constituted with the PSA layer (A) is applied to surfacesof parts (components) formed of various materials, it may show greatadhesion (e.g. peel strength) to these surfaces. Accordingly, in anotheraspect, the present invention provides a PSA sheet-bearing partcomprising a part and a PSA sheet having an adhesive face constitutedwith the acrylic PSA layer, with the adhesive face (surface of theacrylic PSA layer) being adhered to a surface of the part.

A preferable example of the PSA sheet-bearing part comprises a partcomprising an olefinic rubber surface and a PSA sheet having an adhesiveface constituted with the acrylic PSA layer, with the adhesive facebeing adhered to the olefinic rubber surface. As the PSA sheet, a PSAsheet disclosed herein can be preferably used.

Such a PSA sheet-bearing part may be in an embodiment where the adhesiveface is directly applied to the olefinic rubber surface. Herein, to bedirectly applied means that no other layers (primer layer, etc.) arepresent between the adhesive face and the olefinic rubber surface. Incomparison to an embodiment where, for instance, a primer layer ispresent between the olefinic rubber material surface and the adhesiveface, the production process can be simplified for the PSA sheet-bearingpart in such an embodiment, thereby leading to great productivity. Aheretofore typical primer layer is formed by applying a primer solution(a solution containing a primer layer-forming component in an organicsolvent) and allowing it to dry. From the standpoint of reducingenvironmental stress, it is preferable to be able to omit the use ofsuch a solution. In addition, since no device is necessary for theapplication and drying of a primer solution, the production facility forthe PSA sheet-bearing part can be simplified. Furthermore, as it doesnot require a step of drying a primer solution, it is also advantageousin terms of the energy efficiency.

Specific examples of the olefinic rubber surface-bearing part include,but not particularly limited to, vehicle rubber parts such as weatherstrips, moldings including pillar moldings, belt moldings and roofmoldings, bumpers, hoses including radiator hoses and heater hoses,brake couplings, vehicle interior materials and so on; rubber parts forbuildings such as roofing sheets; electric cable jacket materials;conveyor belts; and so on. Herein, a weather strip is a part that isapplied typically to bodies and/or parts of vehicles to seal gapsbetween openings (vehicle doors, windows, trunk lids, bonnets, etc.) andparts that close these openings (door panels, windshields, etc.).Specific examples of the weather strips include so-called door weatherstrips, opening trim weather strips, window weather strips, glass runchannels, etc. The art disclosed herein can be preferably implemented inan embodiment where, for instance, the olefinic rubber surface-bearingpart is a vehicle rubber part (in particular, flexible hollow parts suchas weather strips).

The PSA sheet-bearing part disclosed herein has a peel strength ofpreferably 5 N/10 mm or greater or more preferably 7 N/10 mm or greaterwhen the adhesive face is directly adhered to an olefinic rubber surfaceand the PSA sheet is peeled from the olefinic rubber surface in the 180°direction at a tensile speed of 50 mm/min. Such a PSA sheet-bearing partis preferable since it has a highly reliable joint between the part andthe PSA sheet. From the standpoint of such joint reliability, etc., thepeel strength is preferably 10 N/10 mm or greater, more preferably 15N/10 mm or greater, or yet more preferably 20 N/10 mm or greater.

In a preferable embodiment, the PSA sheet-bearing part may be in anembodiment comprising a double-faced PSA sheet whose both surfaces areformed as adhesive faces and one adhesive face of the double-faced PSAsheet is directly adhered on the olefinic rubber surface of the part.With respect to the PSA sheet-bearing part in such an embodiment, byapplying the other adhesive face of the PSA sheet to a desirablelocation, the olefinic rubber surface-bearing part can be easily fixedto the location. For instance, when the olefinic rubber surface-bearingpart is a vehicle weather strip, the weather strip can be easilyattached to a vehicle body or its component (door panel, etc.).

FIG. 4 schematically illustrates an example of the PSA sheet-bearingpart disclosed herein. PSA sheet-bearing part 50 comprises a PSA sheet 5formed of an acrylic PSA layer (PSA layer (A)) 51 comprising a monomer Ain its monomeric components, and a door weather strip 52 molded(typically co-extruded) in a hollow strip of an olefinic rubbermaterial. The first adhesive face 51A of PSA sheet 5 is a surface of thePSA layer (A) and is directly applied to a surface 52A of door weatherstrip 52. In the PSA sheet-bearing part 50 thus constituted, bypress-bonding the second adhesive face 51B of PSA sheet 5 to a surface60A of a door panel 60, door weather strip 52 can be easily fixed to thedoor panel 60. Even without special heating of the second adhesive face51B of PSA sheet 5 and the surface 60A of door panel 60, thepress-bonding can be done quickly at ordinary temperature.

FIG. 9 shows another example of the PSA sheet-bearing part disclosedherein. PSA sheet-bearing part 50 comprises a PSA sheet 20 having astructure shown in FIG. 4 which corresponds to Configurational Example 4described above and further comprises a door weather strip 52 molded(typically extruded) from an olefinic rubber material into a hollowstrip. The first adhesive face 221A of PSA sheet 20 is a surface of anacrylic PSA layer (preferably a PSA layer (A)) and is directly appliedto the surface 52A of door weather strip 52. In PSA sheet-bearing part50 thus constructed, by press-bonding the second adhesive face 222A ofPSA sheet 20 to a surface 60A of a door panel 60, door weather strip 52can be easily fixed to the door panel 60. The press-bonding can becompleted quickly at ordinary temperature without special heating of thesecond adhesive face 222A of PSA sheet 20 or the surface 60A of doorpanel 60.

A typical weather strip has a long shape (e.g. as long as or longer thanabout 100 cm). Since a weather strip is generally produced by extrusion,it has a linear or gently curved form in its length direction when it isin its free state. Such a weather strip is usually installed in avehicle while it is deformed (curved) in the length direction along aprescribed line marked for installation. Accordingly, it is desirablethat the double-faced PSA sheet for fastening the weather strip ishighly conformable to the deformation. The high conformability of thedouble-faced PSA sheet is especially meaningful when the weather stripis installed in a prescribed location in an embodiment where the PSAsheet-bearing weather strip (PSA sheet-bearing part) is deformed, withone surface of the double-faced PSA sheet being adhered to the weatherstrip, and the other adhesive face is press-bonded to the prescribedlocation of a vehicle body, etc.

When the part is a long rubber part such as a weather strip, as for thePSA sheet that is applied to the part to constitute a PSA sheet-bearingpart, it is particularly preferable to use a PSA sheet that has anadhesive face formed with the PSA layer (A) and comprises at least onebubble-containing layer. The PSA sheet thus constituted is flexiblebecause of the inclusion of the bubble-containing layer and has greatconformability to surface structures and deformation of adherend. Thus,it is preferable as a component of a PSA sheet-bearing strip asdescribed above. With the bubble-containing layer, the PSA sheet alsohas great cushioning properties. This contributes to increase theconformability to a surface structure of a weather strip and it is alsoadvantageous from the standpoints of increasing the conformability to asurface structure (a step, etc.) of the surface to which the weatherstrip is applied, from the standpoint of absorbing variation of gapsbetween the weather strip surface and the surface on which the weatherstrip is attached.

<Method for Producing PSA Sheet-Bearing Part>

As the method for producing the PSA sheet-bearing part disclosed herein,a method can be preferably employed, the method comprising obtaining amolded olefinic rubber body (olefinic rubber part) that has an olefinicrubber surface, obtaining a PSA sheet that has an adhesive face formedwith an acrylic PSA layer, and applying the adhesive face to a surfaceof the molded olefinic rubber body.

In the PSA sheet disclosed herein, the adhesive face formed as thesurface of the acrylic PSA layer (preferably a PSA layer (A)) has greataffinity to an olefinic rubber surface. Accordingly, the adhesive facecan be applied to the molded olefinic rubber body without specialheating of the adhesive face and the surface (the surface to which thePSA sheet is applied, or the “surface subject to adhesion”) of themolded olefinic rubber body; and even when thus applied, it can showgreat adhesion to the molded olefinic rubber body. Alternatively, fromthe standpoint of increasing the productivity, etc., the PSA sheetdisclosed herein can be applied to an olefinic rubber surface in anembodiment where the surface subject to adhesion and/or the adhesiveface are heated. It is usually preferable to employ an embodiment ofapplication where the surface subject to adhesion and the abrasive faceare not especially heated. According to such an embodiment, energy costscan be saved as compared to the heating embodiment. It is alsopreferable because the application can be done with simpler equipmentand the application conditions are also easy to manage. The applicationcan be carried out typically at ordinary temperature (e.g. 0° C. to 50°C., typically in an environment at a temperature of about 10° C. to 40°C.).

When the PSA sheet disclosed herein is used in an embodiment where it isapplied to various types of adherend at ordinary temperature, it mayshow sufficient adhesion to the adherend. On the other hand, the PSAsheet disclosed herein can be applied to an adherend in an embodimentwhere the surface subject to adhesion and/or the adhesive face areheated. For instance, it is preferable to apply an embodiment where thePSA sheet is applied while the temperature (typically almost equal tothe temperature of the surface subject to adhesion) of the adherend ispurposely elevated above ordinary temperature. This can bring about yetgreater peel strength. The heating temperature is not particularlylimited and can be suitably set in view of the balance among the heatresistance of the adherend, workabilities, extent of effects obtainableby heating, and so on. For instance, the temperature of the adherend canbe above 50° C. and is preferably 75° C. or higher, or more preferably100° C. or higher. The upper limit of the heating temperature can be,for instance, 200° C. or lower and is usually suitably 175° C. or lower.Like this embodiment, the technique of applying the PSA sheet to anadherend at an elevated temperature can be preferably applied, forinstance, in application to a low-polar adherend such as an olefinicrubber. It may also produce significant effects when it is applied inapplication to various other types of adherend. The preferabletemperature ranges can be used as the heating temperature for theadherend (surface subject to adhesion) and also as the heatingtemperature for the adhesive face.

The PSA sheet-bearing part production method disclosed herein can bepreferably practiced in an embodiment where the surface (surface subjectto adhesion) of the molded olefinic rubber body is subjected to asuitable cleaning treatment and the adhesive face is applied (preferablydirectly applied) to the cleaned surface. According to such anembodiment, the PSA sheet-bearing part can be produced, with the PSAsheet being more firmly adhered to the olefinic rubber surface.

As the cleaning treatment, a treatment where a cleaning liquid isallowed to make contact with the surface subject to adhesion can bepreferably used. The cleaning liquid used is not particularly limited.For instance, a cleaning liquid comprising an organic solvent can bepreferably used. Examples of the organic solvent include lower alcoholssuch as methyl alcohol, ethyl alcohol, isopropyl alcohol, etc.; lowerketones such as acetone, methyl isobutyl ketone, cyclohexanone, etc.;acetic acid esters such as ethyl acetate, butyl acetate, etc.; acyclicor cyclic amides such as dimethylformamide, dimethylacetamide,2-methylpyrrolidone, etc.; aromatic solvents such as toluene, xylene,etc.; and the like. These can be used singly as one species or in acombination of two or more species. Alternatively, a cleaning liquidcomprising water can be used. For instance, a mixed solvent of anorganic solvent as listed above and water can be preferably used. As itis unlikely to degrade a molded olefinic rubber body and is easy tohandle, it is usually preferable to use a mixed solvent of a loweralcohol or water and another lower alcohol. A preferable example of thecleaning liquid is isopropyl alcohol (IPA).

The cleaning treatment using a cleaning liquid may be, for instance, atreatment where a portion of the molded olefinic rubber body thatincludes the surface subject to adhesion is immersed in the cleaningliquid, a treatment where the surface subject to adhesion (treatedsurface) is wiped with cloth impregnated with the cleaning liquid, atreatment where the cleaning liquid is sprayed to the surface subject toadhesion, and so on. These treatments can be applied singly as one typeor in a combination of two or more types. The extent (immersing time inthe cleaning liquid, number of times to wipe the surface subject toadhesion, spraying rate of the cleaning liquid, etc.) and embodiment ofthe treatment can be suitably selected in view of the purpose andembodiment of the use of the PSA sheet-bearing part. From the standpointof the convenience of the operation, the treatment where the surface istreated with cloth impregnated with the cleaning liquid can bepreferably used. The number of times to wipe the treated surface withcloth with the cleaning liquid can be, but not particularly limited to,for instance, about 1 to 50 times. From the standpoint of theproductivity, etc., it is usually suitably about 1 to 30 times.

With reference to FIG. 10, the PSA sheet-bearing part production methodaccording to a preferable embodiment is described. In particular, atreatment is performed, where a molded olefinic rubber body (e.g. doorweather strip 52 shown in FIG. 9) is obtained and its surface 52A (asurface subject to adhesion) is cleaned with a cleaning liquid (stepS10). For instance, the surface 52A subject to adhesion is wiped withcloth impregnated with the cleaning liquid about 1 to 20 times. To thecleaned surface 52A subject to adhesion, the PSA sheet is press-bonded(step S20). For instance, as shown in FIG. 9, the first adhesive face221A of PSA sheet 20 shown in FIG. 4 is press-bonded to the surface 52Asubject to adhesion. The press-bonding can be carried out in anenvironment at ordinary temperature without special heating of themolded olefinic rubber body and the PSA sheet. In such a manner, a PSAsheet-bearing part in which a PSA sheet is directly bonded to a surfaceof a molded olefinic rubber body can be preferably produced.

Several working examples relating to the present invention are describedbelow, but the present invention is not intended to be limited to theseexamples. In the description below, “parts” and “%” are based on themass unless otherwise specified.

<List of Abbreviations>

In the description below, names of monomers and crosslinking agents aresometimes indicated with the following abbreviations.

[Monomers]

2EHA: 2-ethylhexyl acrylate

BA: n-butyl acrylate

CHA: cyclohexyl acrylate

CHMA: cyclohexyl methacrylate

IBXMA: isobornyl methacrylate

DMAEA: dimethylaminoethyl acrylate

DMAEM: dimethylaminoethyl methacrylate

ACMO: N-acryloylmorpholine

AA: acrylic acid

MAA: methacrylic acid

2HEA: 2-hydroxyethyl acrylate

[Crosslinking Agents]

TMPTA: trimethylolpropane triacrylate

TMP-3P: ethylene oxide-modified trimethylolpropane tri(meth)acrylate(available from Osaka Organic Chemical Industry, Ltd., trade name“VISCOAT 360”)

HDDA: 1,6-hexanediol diacrylate

DPHA: dipentaerythritol hexaacrylate

Experiment 1 Preparation of PSA Sheets Example H1

In a four-neck flask, was placed a monomer mixture consisting of 77.9parts of 2-ethylhexyl acrylate (2EHA), 20.5 parts of cyclohexyl acrylate(CHA) and 1.5 parts of N,N-dimethylaminoethyl methacrylate (DMAEM) alongwith 0.05 part 2,2-dimethoxy-1,2-diphenylethane-1-on (available fromBASF Corporation, trade name “IRGACURE 651”) and 0.05 part of1-hydroxy-cyclohexyl phenyl ketone (available from BASF Corporation,trade name “IRGACURE 184”). In a nitrogen atmosphere, the resultingmixture was exposed to UV rays to undergo partial photopolymerization,whereby syrup (h1) was obtained comprising a polymer having a weightaverage molecular weight (Mw) of 30×10⁴ and unreacted monomers. Theconversion of the monomer mixture in this syrup (h1) was about 30%.

To a monomer mixture consisting of 70 parts of cyclohexyl methacrylate(CHMA) and 30 parts of DEAEM, n-dodecyl mercaptan was added and themixture was purged with nitrogen to remove dissolved oxygen.Subsequently, the mixture was heated to 90° C. and 0.005 part of tradename “PERHEXYL O” and 0.01 part of trade name “PERHEXYL D” bothavailable from NOF Corporation were added as peroxide-based initiators.This was stirred at 90° C. for one hour, heated to 150° C. over onehour, and stirred at 150° C. for one hour. The mixture was then heatedto 170° C. over one hour and stirred at 170° C. for 60 minutes. Themixture was then placed under reduced pressure at 170° C. and stirredfor one hour to remove remaining monomers, whereby an acrylic oligomer(h1) was obtained, having a Mw of 0.5×10⁴.

To 100 parts of the syrup (h1), were added and mixed 20 parts of theoligomer (h1), 0.12 part of TMPTA as a crosslinking agent and 0.30 partof trade name “P-02” available from Soken Chemical & Engineering Co.,Ltd., as a photopolymerization initiator to prepare a PSA compositionaccording to this example.

Two sheets of 38 μm thick polyethylene terephthalate (PET) film wereobtained, with one surface of each sheet being a release that had beenface that had been treated with a silicone-based release agent. To therelease face of the first sheet of PET film, the PSA composition wasapplied to a thickness of 500 μm after light irradiation. To the PSAcomposition applied, the second sheet of PET film was laid over and theresultant was irradiated with UV rays to cure the PSA composition andform a PSA layer. UV ray irradiation was performed with a black light(15 W/cm) at an irradiance of 3 mW/cm² (measured with an industrial UVchecker (available from Topcon Corporation, trade name “UVR-T1” withlight detector model number “UD-T36”) with peak sensitivity at 350 nm inwavelength) for two minutes, and then with a low illuminance metalhalide lamp available from Toshiba Lighting & Technology Corporation atan irradiance of 8 mW/cm² (measured with the UV checker). A PSA sheetwas thus obtained formed of a PSA layer resulting from UV ray-curing ofthe PSA composition. The first and second adhesive faces of the PSAsheet are protected with the two sheets of PET film (release liner),respectively.

In this example, to the monomer mixture to obtain the acrylic oligomer(h1), 6 parts of n-dodecylmercaptan was added relative to 100 parts ofmonomers. In this and other experiments, when preparing an acrylicoligomer other than the acrylic oligomer (h1), the amount of n-dodecylmercaptan was adjusted if needed so as to obtain an acrylic oligomer (b)having a desired Mw.

Example H2

The photopolymerization initiator was changed to 0.25 part of2,2-dimethoxy-1,2-diphenylethane-1-on (available from BASF Corporation,trade name “IRGACURE 651”). Otherwise in the same manner as Example H1,a PSA composition according to this example was prepared. Using this PSAcomposition, but otherwise in the same manner as Example H1, a PSA sheetaccording to this example was obtained.

Example H3

The crosslinking agent was changed to 0.14 part of 1,6-hexanedioldiacrylate (HDDA), but otherwise in the same manner as Example H2, a PSAsheet according to this example was obtained.

Example H4

The crosslinking agent was changed to 0.13 part of dipentaerythritolhexaacrylate (DPHA), but otherwise in the same manner as Example H2, aPSA sheet according to this example was obtained.

Example H5

Using a monomer consisting of 50 parts of CHMA and 50 parts of DEAEM,but otherwise in the same manner as the preparation of the acrylicoligomer (h1), an acrylic oligomer (h5) was obtained having a Mw of0.5×10⁴.

To 100 parts of the syrup (h1) prepared in Example H1, were added andmixed 20 parts of the acrylic oligomer (h5), 0.12 part of TMPTA and 0.20part of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (available fromBASF Japan Ltd., trade name “IRGACURE 819”) as a photopolymerizationinitiator to prepare a PSA composition according to this example. Usingthis PSA composition, but otherwise in the same manner as Example H1, aPSA sheet according to this example was obtained.

Examples H6 to H8

The amounts of photopolymerization initiator were changed to 0.30 part,0.40 part and 0.50 part, but otherwise in the same manner as Example H5,PSA sheets according to Examples H6 to H8 were obtained, respectively.

Example H9

A monomer mixture consisting of 80 parts of 2EHA and 20 parts of CHA wassubjected to partial photopolymerization in the same manner as ExampleH1 to obtain syrup (h9) comprising a polymer having a Mw of 30×10⁴ andunreacted monomers. The monomer conversion was about 30%.

Using solely CHMA as the monomer, but otherwise in the same manner asthe preparation of the acrylic oligomer (h1), an acrylic oligomer (h9)was obtained having a Mw of 0.5×10⁴.

To 100 parts of the syrup (h9), were added and mixed 20 parts of theacrylic oligomer (h9), 0.12 part of TMPTA as a crosslinking agent and0.30 part of trade name “P-02” available from Soken Chemical &Engineering Co., Ltd., as a photopolymerization initiator to prepare aPSA composition according to this example. Using this PSA composition,but otherwise in the same manner as Example H1, a PSA sheet according tothis example was obtained.

[Evaluation of Properties]

(To-EPDM Initial Peel Strength (20-min Peel Strength))

Each PSA sheet obtained above was cut into a 10 mm wide strip tofabricate a measurement sample. The PET film (release liner) coveringits first adhesive face was removed and 50 μm thick PET film with norelease treatment was applied to back the PSA sheet.

The surface of the standard EPDM plate as the adherend was cleaned bywiping twice in one direction with IPA-wet cloth.

In a standard environment at 23° C. and 50% RH, the release linercovering the second adhesive face of the sample was removed and the PSAsheet was press-bonded to the standard EPDM plate after cleaned with a 2kg roller moved back and forth once. This was stored in the standardenvironment for 20 minutes. Subsequently, in the same environment, 180°peel strength (N/10 mm) was measured at a tensile speed of 50 mm/min,using a universal tensile and compression testing machine (availablefrom Minebea Co., Ltd., system name “Tensile/Compression Tester,TG-1kN”), based on JIS Z0237(2004). Two measurements were taken andtheir arithmetic average value wad determined.

(Post-Aging to-EPDM Peel Strength (7-Day Peel Strength))

After the measurement sample was press-bonded to the standard EPDMplate, the time stored in the standard environment was changed from 20minutes to 7 days, but otherwise in the same manner as the measurementof to-EPDM initial peel strength, 180° peel strength (N/10 mm) wasmeasured. Two measurements were taken and their arithmetic average valuewad determined.

(Holding Power)

Each PSA sheet obtained above was cut into a 20 mm wide strip tofabricate a measurement sample. The PET film (release liner) coveringits first adhesive face was removed and 50 μm thick PET film with norelease treatment was applied to back the PSA sheet. Subsequently, therelease liner covering the second adhesive face of the sample wasremoved and the sample was applied at its one end to a stainless steel(SUS) plate as the adherend over a 20 mm wide by 20 mm long bonding areawith a 5 kg roller rolled once in one direction. This was stored in astandard environment at 23° C. and 50% RH for 24 hours. Based on JISZ0237(2004), the SUS plate was then vertically suspended in anenvironment at 40° C. and a 500 g load was applied to the free end ofthe sample. After stored with the load applied thereto for two hours inthe environment at 40° C., the time taken for the sample to peel fromthe SUS plate and fall off was measured.

The measurement was taken using two measurement samples for each PSAsheet and their arithmetic average value was determined.

The results are shown in Table 1. The symbol “-” in the column for thepeel strength measurement results indicates that the peel strength wasnot measured. Table 1 also shows the gel fractions measured by theaforementioned method with respect to the PSA layers constituting thePSA sheets according to the respective examples.

TABLE 1 Ex. H1 H2 H3 H4 H5 H6 H7 H8 H9 Syrup composition (parts) 2EHA77.9 77.9 77.9 77.9 77.9 77.9 77.9 77.9 80 CHA 20.5 20.5 20.5 20.5 20.520.5 20.5 20.5 20 DMAEM 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 — Total 99.999.9 99.9 99.9 99.9 99.9 99.9 99.9 100 Oligomer composition (parts) CHMA70 70 70 70 50 50 50 50 100 DMAEM 30 30 30 30 50 50 50 50 — Total 100100 100 100 100 100 100 100 100 Oligomer Mw (×10⁴) 0.5 0.5 0.5 0.5 0.50.5 0.5 0.5 0.5 PSA composition Syrup 100 100 100 100 100 100 100 100100 (parts) Oligomer 20 20 20 20 20 20 20 20 20 Crosslinking TMPTA 0.120.12 — — 0.12 0.12 0.12 0.12 0.12 agent HDDA — — 0.14 — — — — — — DPHA —— — 0.13 — — — — — Initiator P-02 0.30 — — — — — — — 0.30 Irgacure 819 —— — — 0.20 0.30 0.40 0.50 — Irgacure 651 — 0.25 0.25 0.25 — — — — —m_(A)/m_(T) (%) 6.3 6.3 6.3 6.3 9.6 9.6 9.6 9.6 — A_(O)/A_(S) 4.0 4.04.0 4.0 6.7 6.7 6.7 6.7 — m_(C)/m_(T) (%) 28.8 28.8 28.8 28.8 25.4 25.425.4 25.4 33.3 m_(A)/m_(C) 0.22 0.22 0.22 0.22 0.38 0.38 0.38 0.38 — Gelfraction (%) 45 37 40 35 42 36 30 36 35 to-EPDM peel strength (initial)After 20 min 5.0 7.0 6.2 6.4 7.0 9.0 18.0 9.0 3.2 50 mm/min (N/10 mm)to-EPDM peel strength (aged) After 7 days — — — — 9.0 13.0 19.0 11.0 3.550 mm/min (N/10 mm) Holding power 40° C., 500 g, 2 hr 20 min 5 min 12min 9 min 86 min 27 min 28 min 15 min 6 min (Thickness of PSA sheet: 500μm)

As shown in Table 1, the PSA sheets of Examples H1 to H8 all exhibitedto-EPDM initial peel strength values of 5 N/10 mm or greater, showingexcellent initial adhesion to EPDM. From comparison of Examples H1 andH2 to H4 and comparison of Examples H5 and H6 to H8, when the gelfraction was 40% or lower, the to-EPDM initial peel strength had atendency to increase.

In addition, the PSA sheets of Examples H6 to H8 all exhibited to-EPDMinitial peel strength values of 7 N/10 mm or greater and also post-agingto-EPDM peel strength values of 10 N/10 mm or greater, showing greatadhesion after aged as well.

With respect to the PSA sheets of Examples H5 to H8, their holding time(time taken for their samples to fall in the holding power test) was all15 minutes or longer, showing their sufficient cohesion for practicaluse.

Experiment 2 Example K1

To 100 parts of the syrup (h1) prepared in Example H1, were added andmixed 20 parts of the acrylic oligomer (h1), 0.12 part of TMPTA as acrosslinking agent and 0.20 part ofbis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (e.g. trade name“IRGACURE 819” available from BASF Japan Ltd.) as a photopolymerizationinitiator to prepare a PSA composition according to this example.

Two sheets of 38 μm thick polyethylene terephthalate (PET) film wereobtained, with one surface of each sheet being a release face that hadbeen treated with a silicone-based release agent. To the release face ofthe first sheet of PET film, the PSA composition was applied to athickness of 100 μm after light irradiation. To the PSA compositionapplied, the second sheet of PET film was laid over and the resultantwas irradiated with UV rays to cure the PSA composition and form a PSAlayer. UV ray irradiation was performed with a black light (15 W/cm) atan irradiance of 5 mW/cm² (measured with an industrial UV checker(available from Topcon Corporation, trade name “UVR-T1” with lightdetector model number “UD-T36”) with peak sensitivity at 350 nm inwavelength) at a light dose of 1500 mJ/cm². A PSA sheet was thusobtained formed of a PSA layer resulting from UV ray-curing of the PSAcomposition. The first and second adhesive faces of the PSA sheet areprotected with the two sheets of PET film (release liner), respectively.

Example K2

To 100 parts of the syrup (h1) prepared in Example H1, were added andmixed 20 parts of the acrylic oligomer (h1), 0.12 part of TMPTA as acrosslinking agent, 0.4 part ofbis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (available from BASFJapan Ltd., trade name “IRGACURE 819”) as a photopolymerizationinitiator and 4 parts of glass balloon to prepare a PSA compositionaccording to this example. As the glass balloon, hollow glass beads(made of borosilicate glass, trade name “SPHERICEL® 25P45,” particlediameter range 30 μm to 60 μm, average particle diameter 45 μm, density0.25 g/cm³) available from Potters-Ballotini Co., Ltd., were used. Usingthis PSA composition, but otherwise in the same manner as Example K1, aPSA sheet according to this example was obtained.

Example K3

The amount of the glass balloon was changed to 8 parts to 100 parts ofthe syrup (h1), but otherwise in the same manner as Example K2, a PSAsheet according to this example was obtained.

Example K4

The amount of the glass balloon was changed to 12 parts to 100 parts ofthe syrup (h1), but otherwise in the same manner as Example K2, a PSAsheet according to this example was obtained.

Example K5

To 100 parts of the syrup (h1) prepared in Example H1, were added andmixed 20 parts of the acrylic oligomer (h1), 0.12 part of TMPTA as acrosslinking agent, 0.4 part ofbis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (available from BASFJapan Ltd., trade name “IRGACURE 819”) as a photopolymerizationinitiator and 5 parts of calcium carbonate to prepare a PSA compositionaccording to this example. As the calcium carbonate, heavy calciumcarbonate (average particle diameter 3.2 μm, specific surface area 0.7m²/g) available from Maruo Calcium Co., Ltd., was used. Using this PSAcomposition, but otherwise in the same manner as Example K1, a PSA sheetaccording to this example was obtained.

Example K6 to K8

The amounts of calcium carbonate were changed to 10 parts, 15 parts and20 parts to 100 parts of the syrup (h1), but otherwise in the samemanner as Example K2, PSA sheets according to Examples K6 to K8 wereobtained, respectively.

Example K9

To 100 parts of the syrup (h1) prepared in Example H1, were added andmixed 20 parts of the acrylic oligomer (h1), 0.12 part of TMPTA as acrosslinking agent, 0.4 part ofbis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (available from BASFJapan Ltd., trade name “IRGACURE 819”) as a photopolymerizationinitiator and 12.5 parts of shirasu balloon to prepare a PSA compositionaccording to this example. As the shirasu balloon, trade name “SUPERBALLOON BA-15” (particle diameter range 20 μm to 300 μm, bulk density0.12 g/cm³ to 0.18 g/cm³) available from Showa Chemical Industry Co.,Ltd., was used. Using this PSA composition, but otherwise in the samemanner as Example K1, a PSA sheet according to this example wasobtained.

[Evaluation of Properties]

In the same manner as Experiment 1, they were tested for to-EPDM initialpeel strength, post-aging to-EPDM peel strength and holding power. Theresults are shown in Table 2.

TABLE 2 Ex. K1 K2 K3 K4 K5 K6 K7 K8 K9 Syrup composition (parts) 2EHA77.9 77.9 77.9 77.9 77.9 77.9 77.9 77.9 77.9 CHA 20.5 20.5 20.5 20.520.5 20.5 20.5 20.5 20.5 DMAEM 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5Oligomer composition (parts) CHMA 70 70 70 70 70 70 70 70 70 DMAEM 30 3030 30 30 30 30 30 30 Oligomer Mw (×10⁴) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.50.5 PSA composition Syrup 100 100 100 100 100 100 100 100 100 (parts)Oligomer 20 20 20 20 20 20 20 20 20 Filler Glass balloon — 4 8 12 — — —— — CaCO₃ — — — — 5 10 15 20 — Shirasu balloon — — — — — — — — 12.5Crosslinking TMPTA 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 agentInitiator Irgacure 819 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 m_(A)/m_(T)(%) 6.3 6.3 6.3 6.3 6.3 6.3 6.3 6.3 6.3 A_(O)/A_(S) 4.0 4.0 4.0 4.0 4.04.0 4.0 4.0 4.0 m_(C)/m_(T) (%) 28.8 28.8 28.8 28.8 28.8 28.8 28.8 28.828.8 m_(A)/m_(C) 0.22 0.22 0.22 0.22 0.22 0.22 0.22 0.22 0.22 Gelfraction (%) 20 11 12 15 18 14 18 21 22 to-EPDM peel strength (initial)After 20 min 7.3 11.4 9.9 9.9 12.5 11.5 11.5 11.5 6.8 50 mm/min (N/10mm) to-EPDM peel strength (aged) After 7 days 13.0 9.8 9.0 7.0 10.7 10.410.1 9.5 8.6 50 mm/min (N/10 mm) Holding power 40° C., 500 g, 2 hr 55min 7 min 4 min 4 min 12 min 5 min 4 min 3 min 10 min (Thickness of PSAsheet: 100 μm)

As shown in Table 2, the PSA sheets of Examples K1 to K9 all exhibitedto-EPDM initial peel strength at or above 5 N/10 mm and post-agingto-EPDM peel strength at or above 7 N/10 mm, showing excellent adhesionto EPDM. Particularly great results were obtained in Examples K2 and K5to K8.

Experiment 3 Preparation of PSA Sheets Comprising Bubble-ContainingLayers Example L1 Fabrication of Bubble-Containing Adhesive Layers

To a monomer mixture consisting of 90 parts of 2EHA and 15 parts ofacrylic acid (AA), were added 0.05 part of2,2-dimethoxy-1,2-diphenylethane-1-one (available from BASF Japan Ltd.,“IRGACURE 651”) and 0.05 part of 1-hydroxy-cyclohexyl phenyl ketone(available from BASF Japan Ltd., trade name “IRGACURE 184”) asphotopolymerization initiators. Subsequently, the reaction mixture wasirradiated with UV rays to a monomer conversion of 7.0% to prepare syrup(L1) comprising a polymer having a weight average molecular weight (Mw)of 500×10⁴ and unreacted monomers.

To 100 parts of the syrup (L1), were uniformly mixed 0.10 part ofdipentaerythritol hexaacrylate (DPHA) (available from Nippon Kayaku Co.,Ltd., trade name “KAYARAD DPHA” (97 equivalence of acrylates)) (0.028mol to 100 mol of monomers), 0.03 part of2,2-dimethoxy-1,2-diphenylethane-1-one (available from BASF Japan Ltd.,“IRGACURE 651”) as a photopolymerization initiator and 9.0 part of glassballoon (available from Tokai Kogyo Co. Ltd., trade name “CEL-STARZ-27,” specific gravity 0.27) of 45 μm in average particle diameter. Theresultant was deaerated. After deaerated, was added 0.7 part of afluorine-based surfactant (trade name “SURFLON S-393” available from AGCSeimi Chemical Co., Ltd.; an acrylic copolymer having polyoxyethyleneand fluorinated hydrocarbon side chains; Mw 8300) to prepare a PSAcomposition precursor.

Using a device comprising a stator made of a finely toothed disc with acentral open hole and a rotor opposing the stator and similarly made ofa finely toothed disc, the PSA composition precursor was poured betweenthe teeth on the stator and the teeth on the rotor. While spinning therotor at a high speed, nitrogen was introduced into the PSA compositionprecursor via the open hole. By this, bubbles were mixed in the PSAcomposition precursor to prepare a bubble-containing PSA composition.Bubbles were mixed to about 20% by volume with respect to the totalvolume of the bubble-containing PSA composition.

Two sheets of 38 μm thick polyethylene terephthalate (PET) film wereobtained with one face thereof being a release face treated with asilicone-based release agent. To the bubble-containing PSA composition2B, was added 0.03 part of “IRGACURE 651” and was further added 0.5 partof an antioxidant (available from BASF Japan Ltd., “IRGANOX 1010”) and0.02 part of pigment (available from Dainichiseika Color and ChemicalsMfg. Co., Ltd., trade name “AT DN101”) and mixed. This was applied tothe release face of the first sheet of PET film to a thickness of 1.2 mmafter light irradiation. To the PSA composition applied, the secondsheet of PET film was laid over and the resultant was irradiated with UVrays to cure the bubble-containing PSA composition to form a 1.2 mmthick bubble-containing PSA layer. UV ray irradiation was performed fora time period needed to reach a monomer conversion of 99%, using a blacklight at an irradiance of 5 mW/cm² (measured with an industrial UVchecker (available from Topcon Corporation, trade name “UVR-T1” withlight detector model number “UD-T36”) with peak sensitivity at 350 nm inwavelength).

Fabrication of Bubble-Free Adhesive Layers:

A monomer mixture consisting of 37.9 parts of 2EHA, 37.9 parts ofn-butyl acrylate (BA), 21.1 parts of CHA and 3.1 parts of DMAEM wassubjected to partial photopolymerization in the same manner as ExampleH1 to obtain syrup (L1) comprising a polymer having a Mw of 70×10⁴ andunreacted monomers. The monomer conversion was about 30%.

To 100 parts of the syrup (L1), were added and mixed 20 parts of theacrylic oligomer (h1), 0.12 part of TMPTA and 0.30 part of aphotopolymerization initiator (trade name “P-02”) available from SokenChemical & Engineering Co., Ltd., to prepare a PSA composition accordingto this example.

Two sheets of 38 μm thick polyethylene terephthalate (PET) film wereobtained, with one surface of each sheet being a release face that hadbeen treated with a silicone-based release agent. To the release face ofthe first sheet of PET film, the PSA composition was applied to athickness of 40 μm after light irradiation. To the PSA compositionapplied, the second sheet of PET film was laid over and the resultantwas irradiated with UV rays to cure the PSA composition. UV rayirradiation was performed with a black light (15 W/cm) at an irradianceof 5 mW/cm² (measured with an industrial UV checker (available fromTopcon Corporation, trade name “UVR-T1” with light detector model number“UD-T36”) with peak sensitivity at 350 nm in wavelength) at a light doseof 1500 mJ/cm². A 40 μm thick PSA sheet (L1) was thus obtained. The PSAsheet (L1) is formed of a bubble-free adhesive layer (PSA layer (A))comprising a monomer A in its monomeric components.

Preparation of PSA Sheet Comprising Bubble-Containing Layer:

To one surface of the bubble-containing adhesive layer (1.2 mm thick)prepared above, the PSA sheet (L1) (40 μm thick) prepared above wasadhered. A PSA sheet having a total thickness of about 1.24 mm was thusobtained, comprising a bubble-containing adhesive layer and abubble-free adhesive layer (PSA layer (A)) overlaid on one face thereof.

Example L2 Fabrication of Bubble-Free Adhesive Layer

A monomer mixture consisting of 91 parts of 2EHA and 9 parts of acrylicacid (AA) was subjected to partial photopolymerization in the samemanner as Example H1 to obtain syrup (L2) comprising a polymer having aMw of 115×10⁴ and unreacted monomers.

To 100 parts of the syrup (L2), were added and mixed 0.12 part of TMPTAand 0.30 part of a photopolymerization initiator (trade name “P-02”)available from Soken Chemical & Engineering Co., Ltd., to prepare a PSAcomposition according to this example.

This composition was allowed to cure in the same manner as thefabrication of the bubble-free adhesive layer in Example L1 to obtain a40 μm thick PSA sheet (L2). This PSA sheet (L2) is formed of thebubble-free adhesive layer whose monomeric components are free of amonomer A.

Preparation of PSA Sheet Comprising Bubble-Containing Layer:

To one surface of the bubble-containing adhesive layer (1.2 mm thick)prepared in Example L1, in place of the PSA sheet (L1) prepared inExample L1, the PSA sheet (L2) was adhered. Otherwise in the same manneras Example L1, a PSA sheet having a total thickness of about 1.24 mm wasobtained, comprising a bubble-containing adhesive layer and abubble-free adhesive layer overlaid on one face thereof.

[Evaluation of Properties] (To-EPDM Initial Peel Strength)

The standard EPDM plate surface was wiped ten times in one directionwith IPA-wet cloth and the measurement samples were press-bonded to thestandard EPDM plate with a 5 kg roller moved back and forth once.Otherwise in the same manner as Experiment 1, 180° peel strength (N/10mm) was measured. The measurement was taken twice for each and theirarithmetic average value was determined. The results are shown in Table3.

TABLE 3 Ex. L1 L2 Bubble-containing Syrup 2EHA 90 90 adhesive layercomposition (parts) AA 10 10 (1.2 mm thick) PSA Syrup 100 100composition Crosslinking DPHA 0.10 0.10 (parts) agent Initiator Irgacure651 0.06 0.06 Filler Z-27 9.0 9.0 Surfactant S-393 0.7 0.7 AntioxidantIrganox 1010 0.5 0.5 Pigment AT DN101 0.02 0.02 Bubble-free Syrup 2EHA37.9 91 adhesive layer composition (parts) BA 37.9 — (40 μm thick) CHA21.1 — DMAEM 3.1 — AA — 9 Oligomer CHMA 70 — composition (parts) DMAEM30 — Oligomer Mw (×10⁴) 0.5 — PSA Syrup 100 100 composition Oligomer 20— (parts) Crosslinking TMPTA 0.12 0.12 agent Initiator P-02 0.30 0.30to-EPDM initial peel strength Cleaned After 20 min 20.9 8.5 50 mm/min(N/10 mm)

As shown in the table, the PSA sheet of Example L1 exhibited highinitial peel strength to EPDM. It was also confirmed that clearly atleast 10 N/10 mm of to-EPDM peel strength could be obtained even whenthe standard EPDM plate surface was wiped two times instead of tentimes.

The PSA sheet according to Example L1 was further subjected to thefollowing tests. As the adherend, standard EPDM pieces were used. Afterthe adherend surface was cleaned by wiping 10 times in one directionwith IPA-wet cloth and the surface of the bubble-free adhesive layer ofthe PSA sheet according to Example L1 was press-bonded to the cleanedadherend surface. The peel strength was measured after 20 minutes fromthe press-bonding. The results are shown in Table 4. In Table 4, in thecolumn for “Initial Peel Strength,” the values of to-EPDM initial peelstrength measured above are shown.

(Peel Strength in Normal State)

Each PSA sheet was cut into a 10 mm wide strip to prepare a measurementsample. The PET film (release liner) covering its first adhesive face(the surface of the bubble-containing adhesive layer) was removed and 50μm thick PET film with no release treatment was applied to back the PSAsheet. In a standard environment at 23° C. and 50% RH, the release linercovering the second adhesive face (the surface of the bubble-freeadhesive layer) of the sample was removed and the PSA sheet waspress-bonded to the adherend with a 5 kg roller moved back and forthonce. This was stored in the standard environment for 72 hours.Subsequently, in the same environment, 180° peel strength (normal-statepeel strength in N/10 mm) was measured at a tensile speed of 50 mm/min,using a universal tensile and compression testing machine (availablefrom Minebea Co., Ltd., system name “Tensile/Compression Tester,TG-1kN”), based on JIS Z0237(2004).

(Peel Strength at High Temperature)

The peel test environment was changed from the standard environment toan environment at 80° C., but otherwise in the same manner as for thenormal-state peel strength, 180° peel strength (high-temperature peelstrength in N/10 mm) was measured.

(Heat-Resistant Peel Strength)

In the same manner as for the initial peel strength, the PSA sheet waspress-bonded to the adherend and the resultant was stored in thestandard environment for 72 hours and then in an environment at 80° C.for 7 days. After this was store in the standard environment for oneday, 180° peel strength (heat-resistant peel strength in N/10 mm) wasmeasured in the same environment in the same manner as for the initialpeel strength.

(Initial Peel Strength at Low Temperature)

In the measurement of initial peel strength, the environment in whichthe PSA sheet was adherend to the adherend, environment in which it wasstored after press-bonded and environment in which the peel strength wasmeasured were changed from the standard environment to an environment at5° C. Otherwise in the same manner as for the initial peel strength,180° peel strength (low-temperature initial peel strength in N/10 mm)was measured.

(Peel Strength Upon Storage in Humid Conditions)

In the same manner as for the initial peel strength, the PSA sheet waspress-bonded to the adherend and the resultant was stored in thestandard environment for 72 hours and then in hot and humid conditionsat 50° C. and 98% RH for 7 days. After this was store in the standardenvironment for one day, 180° peel strength (post-moisturization peelstrength in N/10 mm) was measured in the same environment in the samemanner as for the initial peel strength.

(Peel Strength Upon Immersion/Storage in Warm Water)

In the same manner as for the initial peel strength, the PSA sheet waspress-bonded to the adherend and the resultant was stored in thestandard environment for 72 hours and then in water at 40° C. for 7days. This was removed from water and stored in the standard environmentfor one say. After this, 180° peel strength (peel strength after warmwater immersion in N/10 mm) was measured in the same environment in thesame manner as for the initial peel strength.

The respective measurements were carried out twice. Table 4 shows theirarithmetic average values.

TABLE 4 to-EPDM peel strength Peel Press-bonding Measurement 50 mm/minstrength tested temperature Storage conditions temperature (N/10 mm)Initial 23° C. Stored at 23° C. for 20 min 23° C. 20.9 In normal state23° C. Stored at 23° C. for 72 hr 23° C. 20.9 At high temp. 23° C.Stored at 23° C. for 72 hr 80° C. 10.4 Heat-resistant 23° C. Stored at23° C. for 72 hr 23° C. 27.8# then stored at 80° C. for 7 days thenstored at 23° C. for 1 day Initial, at  5° C. Stored at 5° C. for 20 min 5° C. 22.2 low temp. Post-moisturization 23° C. Stored at 23° C. for 72hr 23° C. 21.2 then stored at 50° C., 98% RH for 7 days then stored at23° C. for 1 day Upon immersion in 23° C. Stored at 23° C. for 72 hr,23° C. 20.7 warm water then stored/immersed in water at 40° C. for 7days then stored at 23° C. for 1 day *The symbol “#” following a peelstrength value indicates cohesive failure.

As shown in the table, it has been confirmed that the PSA sheetaccording to Example L1 shows excellent adhesion to EPDM under varioustest conditions.

Experiment 4 Preparation of PSA Sheets Example A1

In a four-neck flask, was placed a monomer mixture consisting of 78parts of 2-ethylhexyl acrylate (2EHA), 20 parts of n-butyl acrylate (BA)and 2 parts of N-dimethylaminoethyl acrylate (DMAEA) along with 0.05part 2,2-dimethoxy-1,2-diphenylethane-1-on (available from BASFCorporation, trade name “IRGACURE 651”) and 0.05 part of1-hydroxycyclohexyl phenyl ketone (available from BASF Corporation,trade name “IRGACURE 184”). In a nitrogen atmosphere, the resultingmixture was exposed to UV rays to undergo partial photopolymerization,whereby syrup (a1) was obtained comprising a polymer having a weightaverage molecular weight (Mw) of 45×10⁴ and unreacted monomers. Theconversion of the monomer mixture in this syrup (a1) was about 30%.

To 100 parts of the syrup (a1), were added and mixed 0.10 part oftrimethylolpropane triacrylate (TMPTA) and 0.12 part of2,2-dimethoxy-1,2-diphenylethane-1-on (available from BASF Corporation,trade name “IRGACURE 651”) to prepare a PSA composition according tothis example.

Two sheets of 38 μm thick polyethylene terephthalate (PET) film wereobtained, with one surface of each sheet being a release face that hadbeen treated with a silicone-based release agent. To the release face ofthe first sheet of PET film, the PSA composition was applied to athickness of 40 μm after light irradiation. To the PSA compositionapplied, the second sheet of PET film was laid over and the resultantwas irradiated with UV rays to cure the PSA composition and form a PSAlayer. UV ray irradiation was performed with a black light (15 W/cm) atan irradiance of 5 mW/cm² (measured with an industrial UV checker(available from Topcon Corporation, trade name “UVR-T1” with lightdetector model number “UD-T36”) with peak sensitivity at 350 nm inwavelength) at a light dose of 1500 mJ/cm². A PSA sheet was thusobtained formed of a PSA layer resulting from UV ray-curing of the PSAcomposition. The first and second adhesive faces of the PSA sheet areprotected with the two sheets of PET film (release liner), respectively.

In the PSA layer (PSA sheet), 2.0% of the monomeric components of allpolymers in the PSA layer is attributed to the mass of an aminogroup-containing (meth)acrylate (DMAEA herein). That is, the ratio(m_(A)/m_(T)) of mass (m_(A)) of amino group-containing (meth)acrylateto mass (m_(T)) of monomeric components of all the polymers is 2.0%.

Example A2

Using a monomer mixture consisting of 76 parts of 2EHA, 20 parts of BAand 4 parts of DMAEA, but otherwise in the same manner as Example A1,syrup (a2) was obtained comprising a polymer having a Mw of 34×10⁴ andunreacted monomers. Using the syrup (a2), a PSA composition wasprepared, applied and irradiated with UV rays in the same manner asExample A1 to obtain a PSA sheet according to this example. In the PSAlayer (PSA sheet), 4.0% of the monomeric components of all polymers inthe PSA layer is an amino group-containing (meth)acrylate (DMAEAherein).

Example A3

Using a monomer mixture comprising 2 parts of N,N-dimethylaminoethylmethacrylate (DMAEM) in place of DMAEA, but otherwise in the same manneras Example A1, syrup (a3) was obtained comprising a polymer having a Mwof 54×10⁴ and unreacted monomers. Using the syrup (a3), a PSAcomposition was prepared, applied and irradiated with UV rays in thesame manner as Example A1 to obtain a PSA sheet according to thisexample. In the PSA layer (PSA sheet), 2.0% of the monomeric componentsof all polymers in the PSA layer is an amino group-containing(meth)acrylate (DMAEM herein).

Example A4

Using a monomer mixture consisting of 76 parts of 2EHA, 20 parts of BA,4 parts of acrylic acid (AA) and 0.15 part of 2-hydroxyethyl acrylate(2HEA), but otherwise in the same manner as Example A1, syrup (a4) wasobtained comprising a polymer having a Mw of 115×10⁴ and unreactedmonomers. Using the syrup (a4), a PSA composition was prepared, appliedand irradiated with UV rays in the same manner as Example A1 to obtain aPSA sheet according to this example.

Example A5

Using a monomer mixture comprising 2 parts of N-acryloylmorpholine(ACMO) in place of DMAEA, but otherwise in the same manner as ExampleA1, syrup (a5) was obtained comprising a polymer having a Mw of 68×10⁴and unreacted monomers. Using the syrup (a3), a PSA composition wasprepared, applied and irradiated with UV rays in the same manner asExample A1 to obtain a PSA sheet according to this example.

[Evaluation of Properties]

(To-EPDM Peel Strength at Tensile Speed 300 mm/min)

Using a standard EPDM piece described earlier as the adherend, 180°adhesive strength (to-EPDM peel strength) was measured by the followingprocedure. In particular, each PSA sheet obtained above was cut into a10 mm wide strip to fabricate a measurement sample. The PET film(release liner) covering its first adhesive face was removed and 25 μmthick PET film with no release treatment was applied to back the PSAsheet. In a standard environment at 23° C. and 50% RH, the release linercovering the second adhesive face of the sample was removed and the PSAsheet was press-bonded to the adherend with a 2 kg roller moved back andforth once. This was stored in the standard environment for a prescribedtime period. Subsequently, in the same environment, 180° peel strength(N/10 mm) was measured at a tensile speed of 300 mm/min, using auniversal tensile and compression testing machine (available fromMinebea Co., Ltd., system name “Tensile/Compression Tester, TG-1kN”),based on JIS Z0237(2004).

The peel strength was measured after 30 minutes and after 7 days fromthe press-bonding of the PSA sheets for the following two cases: (1) thePSA sheet was press-bonded to the adherend surface as it was (i.e.without the cleaning treatment) and (2) the PSA sheet was press-bondedafter the adherend surface was wiped twice in one direction with IPA-wetcloth.

The results are shown in Table 5.

TABLE 5 Ex. A1 A2 A3 A4 A5 Syrup composition (parts) 2EHA 78 76 78 76 78BA 20 20 20 20 20 DMAEA 2 4 — — — DMAEM — — 2 — — ACMO — — — — 2 AA — —— 4 — 2HEA — — — 0.15 — Total 100 100 100 100.15 100 PSA compositionSyrup 100 100 100 100 100 (parts) Crosslinking TMPTA 0.10 0.10 0.10 0.100.10 agent Initiator Irgacure 651 0.12 0.12 0.12 0.12 0.12 m_(A)/m_(T)(%) 2.0 4.0 2.0 — — to-EPDM Not cleaned After 30 min 1.8 2.2 2.7 1.0 1.8Peel strength After 7 days 1.5 1.7 2.5 1.4 1.0 300 mm/min Cleaned After30 min 2.6 2.7 2.7 1.5 2.3 (N/10 mm) After 7 days 2.8 2.5 4.5 1.5 2.2(Thickness of PSA sheet: 40 μm)

As shown in the table, with respect to the PSA sheets of Examples A1 toA3 obtained using the syrup (polymerization product (a)) as thepartially-polymerized product of a monomer mixture comprising an aminogroup-containing (meth)acrylate (monomer A), their adhesion (peelstrength) to EPDM was clearly high as the adherend when compared to thePSA sheets of Examples A4 and A5 with each comprising no monomer A inits monomeric components. More specifically, as compared to Example A4using AA and 2HEA in place of the monomer A, with or without cleaningtreatment, the peel strength was higher both initially (after 30minutes) and after aged (after 7 days). They also exhibited greateradhesion to EPDM even when compared to Example A5 using an amidegroup-containing (meth)acrylate (ACMO) in place of the monomer A. Inparticular, with respect to EPDM after cleaned, more significant effectsof the use of the monomer A to improve the adhesion to EPDM wasobserved.

In Example A3 using DMAEM among monomers A, as compared to Examples A1and A2 using DMAEA, more preferable results were obtained as its peelstrength decreased less with time without cleaning treatment andincreased with time with cleaning treatment.

Experiment 5 Preparation of PSA Sheets Example B1

A monomer mixture consisting of 76 parts of 2EHA, 20 parts of BA, 4parts of AA and 0.15 part of 2HEA was subjected to partialphotopolymerization in the same manner as Example A1 to obtain syrup(b1) comprising a polymer having a Mw of 115×10⁴ and unreacted monomers.

To a monomer mixture consisting of 97 parts of cyclohexyl methacrylate(CHMA) and 3 parts of DEAEM, n-dodecyl mercaptan was added and themixture was purged with nitrogen to remove dissolved oxygen.Subsequently, the mixture was heated to 90° C. and 0.005 part of tradename “PERHEXYL O” and 0.01 part of trade name “PERHEXYL D” bothavailable from NOF Corporation were added as peroxide-based initiators.This was stirred at 90° C. for one hour, heated to 150° C. over onehour, and stirred at 150° C. for one hour. The mixture was then heatedto 170° C. over one hour and stirred at 170° C. for 60 minutes. Themixture was then placed under reduced pressure at 170° C. and stirredfor one hour to remove remaining monomers, whereby an acrylic oligomer(h1) was obtained, having a Mw of 0.2×10⁴.

To 100 parts of the syrup (b1), were added and mixed 20 parts of theoligomer (b1), 0.10 part of TMPTA and 0.10 part of2,2-dimethoxy-1,2-diphenylethane-1-on (available from BASF Corporation,trade name “IRGACURE 651”) to prepare a PSA composition according tothis example.

Using this PSA composition, but otherwise in the same manner as ExampleA1, a PSA sheet according to this example was obtained. In this PSAsheet, the ratio (m_(A)/m_(T)) of mass (m_(A)) of amino group-containing(meth)acrylate (DMAEM herein) to mass (m_(T)) of monomeric components ofall polymers in the PSA layer is 0.5%. The ratio (m_(C)/m_(T)) of mass(m_(C)) of cycloalkyl (meth)acrylate (CHMA herein) to m_(T) is 16.2%.

Examples B2 to B5

In preparing the acrylic oligomer (b1), the amount of n-dodecylmercaptan was adjusted to obtain acrylic oligomers (b2) to (b5) havingMw values shown in Table 6. Using these oligomers (b2) to (b5), butotherwise in the same manner as Example B1, PSA sheets according toExamples B2 to B5 were obtained.

Example B6

Using a monomer mixture consisting of 94 parts of CHMA and 6 parts ofDEAEM, but otherwise in the same manner as the preparation of theacrylic oligomer (b1), an acrylic oligomer (b6) was obtained, having aMw of 0.6×10⁴. Using this oligomer (b6), but otherwise in the samemanner as Example B1, a PSA sheet according to this example wasobtained.

Example B7

Using a monomer mixture consisting of 91 parts of CHMA and 9 parts ofDEAEM, but otherwise in the same manner as the preparation of theacrylic oligomer (b1), an acrylic oligomer (b7) was obtained, having aMw of 0.63×10⁴. Using this oligomer (b7), but otherwise in the samemanner as Example B1, a PSA sheet according to this example wasobtained.

Example B8

Using solely CHMA as the monomer, but otherwise in the same manner asthe preparation of the acrylic oligomer 1), an acrylic oligomer (b8) wasobtained, having a Mw of 0.5×10⁴. Using this oligomer (b8), butotherwise in the same manner as Example B1, a PSA sheet according tothis example was obtained.

[Evaluation of Properties]

(To-EPDM Peel Strength at Tensile Speed 300 mm/min)

The respective PSA sheets obtained above were measured for to-EPDM peelstrength in the same manner as in Experiment 4.

The results are shown in Table 6.

TABLE 6 Ex. B1 B2 B3 B4 B5 B6 B7 B8 Syrup composition (parts) 2EHA 76 7676 76 76 76 76 76 BA 20 20 20 20 20 20 20 20 AA 4 4 4 4 4 4 4 4 2HEA0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 Total 100.15 100.15 100.15100.15 100.15 100.15 100.15 100.15 Oligomer composition (parts) CHMA 9797 97 97 97 94 91 100 DMAEM 3 3 3 3 3 6 9 — Total 100 100 100 100 100100 100 100 Oligomer Mw (×10⁴) 0.2 0.3 0.54 0.7 1 0.6 0.63 0.5 PSAcomposition Syrup 100 100 100 100 100 100 100 100 (parts) Oligomer 20 2020 20 20 20 20 20 Crosslinking TMPTA 0.10 0.10 0.10 0.10 0.10 0.10 0.100.10 agent Initiator Irgacure 651 0.10 0.10 0.10 0.10 0.10 0.10 0.100.10 m_(A)/m_(T) (%) 0.5 0.5 0.5 0.5 0.5 1.0 1.5 — m_(C)/m_(T) (%) 16.216.2 16.2 16.2 16.2 15.7 15.2 16.7 m_(A)/m_(C) 0.03 0.03 0.03 0.03 0.030.06 0.10 — to-EPDM Not cleaned After 30 min 1.8 1.7 1.3 1.5 1.1 1.7 1.01.1 Peel strength After 7 days 2.0 1.7 1.7 1.6 1.5 1.7 2.3 1.0 300mm/min Cleaned After 30 min 2.8 1.9 1.8 1.4 1.5 1.8 1.5 1.3 (N/10 mm)After 7 days 2.3 3.1 2.9 2.6 2.2 2.5 2.3 1.9 (Thickness of PSA sheet: 40μm)

As shown in the table, with respect to the PSA sheets of B1 to B7obtained using PSA compositions each prepared by mixing apartially-polymerized product (syrup) of a monomer mixture and anoligomer comprising a monomer A-derived monomer unit, they exhibitedgreater to-EPDM adhesion, with or without cleaning treatment, ascompared to the PSA sheet of Example B8 obtained with the use of a PSAcomposition free of a monomer A-derived monomer unit. More specifically,the PSA sheets of Examples B1 to B7 exhibited peel strength comparableto or higher than Example B8 initially (after 30 minutes) and clearlyhigher peel strength than Example B8 when aged (after 7 days). In otherwords, the effect of the use of monomer A to increase the to-EPDM peelstrength was observed even in an initial stage and had a tendency toincrease when aged. From comparison of Examples B1 to B5, it is evidentthat in a Mw range of 0.2×10⁴ or higher, with decreasing Mw of theoligomer used, the effect to increase the to-EPDM peel strength(especially the initial peel strength) had a general tendency toincrease.

Experiment 6 Preparation of PSA Sheets Example C1

A monomer mixture consisting of 78 parts of 2EHA, 20 parts of cyclohexylacrylate (CHA) and 2 parts of DMAEM was subjected to partialphotopolymerization in the same manner as Example A1 to obtain syrup(c1) comprising a polymer having a weight average molecular weight (Mw)of 30×10⁴ and unreacted monomers. The conversion of the monomer mixturein the syrup (c1) was about 30%.

To 100 parts of the syrup (c1), were added and mixed 0.16 part of TMPTAand 0.12 part of 2,2-dimethoxy-1,2-diphenylethane-1-on (available fromBASF Corporation, trade name “IRGACURE 651”) to prepare a PSAcomposition according to this example. Using this PSA composition, at alight dose of 3000 mJ/cm², but otherwise in the same manner as ExampleA1, a PSA sheet according to this example was obtained.

In the PSA layer constituting this PSA sheet, the ratio (m_(A)/m_(T)) ofmass (m_(A)) of amino group-containing (meth)acrylate (DMAEM herein) tomass (m_(T)) of all monomeric components is 2.0%. The ratio(m_(C)/m_(T)) of mass (m_(C)) of cycloalkyl (meth)acrylate (CHA herein)to m_(T) is 20.0%. The ratio (m_(A)/m_(C)) of mass (m_(A)) of aminogroup-containing (meth)acrylate to mass (m_(C)) of cycloalkyl(meth)acrylate in the monomeric components of the PSA layer is 0.10.

Example C2

Using a monomer mixture consisting of 97 parts of CHMA and 3 parts ofmethacrylic acid (MAA), but otherwise in the same manner as thepreparation of the acrylic oligomer (b1), an acrylic oligomer (c2) wasobtained, having a Mw of 0.35×10⁴.

To 100 parts of the syrup (c1) prepared in Example C1, were added andmixed 20 parts of the oligomer (c2), 0.16 part of TMPTA and 0.10 part of2,2-dimethoxy-1,2-diphenylethane-1-on (available from BASF Corporation,trade name “IRGACURE 651”) to prepare a PSA composition according tothis example. Using this PSA composition, but otherwise in the samemanner as Example C1, a PSA sheet according to this example wasobtained.

Example C3

Using a monomer mixture consisting of 97 parts of CHMA and 3 parts ofDEAEM, but otherwise in the same manner as the preparation of theacrylic oligomer (b1), an acrylic oligomer (c3) was obtained, having aMw of 0.5×10⁴.

To 100 parts of the syrup (c1) prepared in Example C1, were added andmixed 20 parts of the oligomer (c3), 0.16 part of TMPTA and 0.10 part of2,2-dimethoxy-1,2-diphenylethane-1-on (available from BASF Corporation,trade name “IRGACURE 651”) to prepare a PSA composition according tothis example. Using this PSA composition, but otherwise in the samemanner as Example C1, a PSA sheet according to this example wasobtained. In the PSA layer constituting this PSA sheet, the ratio(m_(A)/m_(T)) of mass (m_(A)) of DMAEM to mass (m_(T)) of monomericcomponents of all polymers is 2.2%. The ratio (A_(O)/A_(S)) of mass(A_(O)) of oligomer (c3)-derived DMAEM to mass (As) of syrup(c1)-derived DMAEM is 0.3.

Example C4

Using a monomer mixture consisting of 70 parts of CHMA and 30 parts ofDEAEM, but otherwise in the same manner as the preparation of theacrylic oligomer (b1), an acrylic oligomer (c4) was obtained, having aMw of 0.5×10⁴.

To 100 parts of the syrup (c1) prepared in Example C1, were added andmixed 20 parts of the oligomer (c4), 0.16 part of TMPTA and 0.12 part of2,2-dimethoxy-1,2-diphenylethane-1-on (available from BASF Corporation,trade name “IRGACURE 651”) to prepare a PSA composition according tothis example. Using this PSA composition, but otherwise in the samemanner as Example C1, a PSA sheet according to this example wasobtained.

To the monomer mixture to obtain the acrylic oligomer (c4) in thisexample, for 100 parts of monomers, 6 parts of n-dodecyl mercaptan wasadded. In this and other experiments, when preparing an acrylic oligomerother than the acrylic oligomer (c4), the amount of n-dodecyl mercaptanwas adjusted if needed so as to obtain an acrylic oligomer (b) having adesired Mw.

Example C5

Using a monomer mixture consisting of 50 parts of CHMA and 50 parts ofDEAEM, but otherwise in the same manner as the preparation of theacrylic oligomer (h1), an acrylic oligomer (c5) was obtained, having aMw of 0.5×10⁴.

Using this oligomer (c5), but otherwise in the same manner as ExampleC4, a PSA composition according to this example was prepared. Using thisPSA composition, but otherwise in the same manner as Example C1, a PSAsheet according to this example was obtained.

Example C6

A monomer mixture consisting of 76 parts of 2EHA, 20 parts of CHA and 4parts of DMAEM was used, but otherwise in the same manner as thepreparation of the syrup (c1), syrup (c6) was obtained comprising apolymer having a weight average molecular weight (Mw) of 30×10⁴ andunreacted monomers. The monomer conversion was 30%.

To 100 parts of the syrup (c6), were added and mixed 0.16 part of TMPTAand 0.10 part of 2,2-dimethoxy-1,2-diphenylethane-1-on (available fromBASF Corporation, trade name “IRGACURE 651”) to prepare a PSAcomposition according to this example. Using this PSA composition, butotherwise in the same manner as Example C1, a PSA sheet according tothis example was obtained.

Example C7

To 100 parts of the syrup (c6) prepared in Example C6, were added andmixed 20 parts of the oligomer (c4) prepared in Example C4, 0.16 part ofTMPTA and 0.10 part of 2,2-dimethoxy-1,2-diphenylethane-1-on (availablefrom BASF Corporation, trade name “IRGACURE 651”) to prepare a PSAcomposition according to this example. Using this PSA composition, butotherwise in the same manner as Example C1, a PSA sheet according tothis example was obtained.

Example C8

Using the oligomer (c5) in place of the oligomer (c4), but otherwise inthe same manner as Example C7, a PSA sheet according to this example wasobtained.

Example C9

A monomer mixture consisting of 80 parts of 2EHA and 20 parts of CHA wasused, but otherwise in the same manner as the preparation of the syrup(c1), syrup (c9) was obtained, comprising a polymer having a weightaverage molecular weight (Mw) of 30×10⁴ and unreacted monomers. Themonomer conversion was 30%.

To 100 parts of the syrup (c9), were added and mixed 20 parts of theoligomer (c2) prepared in Example C2, 0.16 part of TMPTA and 0.12 partof 2,2-dimethoxy-1,2-diphenylethane-1-on (available from BASFCorporation, trade name “IRGACURE 651”) to prepare a PSA compositionaccording to this example. Using this PSA composition, but otherwise inthe same manner as Example C1, a PSA sheet according to this example wasobtained.

[Evaluation of Properties]

(To-EPDM Peel Strength at Tensile Speed 300 mm/min)

The respective PSA sheets obtained above were measured for to-EPDM peelstrength in the same manner as in Experiment 4. In this experiment, peelstrength was measured just after 30 minutes from the press-bonding, withrespect to the adherend cleaned by wiping twice in one direction withIPA-wet cloth.

The results are shown in Table 7.

TABLE 7 Ex. C1 C2 C3 C4 C5 C6 C7 C8 C9 Syrup composition (parts) 2EHA 7878 78 78 78 76 76 76 80 CHA 20 20 20 20 20 20 20 20 20 DMAEM 2 2 2 2 2 44 4 — Total 100 100 100 100 100 100 100 100 100 Oligomer composition(parts) CHMA — 97 97 70 50 — 70 50 97 DMAEM — — 3 30 50 — 30 50 — MAA —3 — — — — — — 3 Total — 100 100 100 100 — 100 100 100 Oligomer Mw (×10⁴)— 0.35 0.5 0.5 0.5 — 0.5 0.5 0.5 PSA composition Syrup 100 100 100 100100 100 100 100 100 (parts) Oligomer — 20 20 20 20 0 20 20 20Crosslinking TMPTA 0.16 0.16 0.16 0.16 0.16 0.16 0.16 0.16 0.16 agentInitiator Irgacure 651 0.12 0.10 0.10 0.12 0.12 0.10 0.10 0.10 0.12m_(A)/m_(T) (%) 2.0 1.7 2.2 6.7 10.0 4.0 8.3 11.7 — A_(O)/A_(S) — — 0.33.0 5.0 — 1.5 2.5 — m_(C)/m_(T) (%) 20.0 32.8 32.8 28.3 25.0 20.0 28.325.0 32.8 m_(A)/m_(C) 0.10 0.05 0.07 0.24 0.40 0.20 0.29 0.47 — to-EPDMPeel strength Cleand 2.0 1.9 2.9 4.2 3.3 2.5 3.0 4.0 1.2 300 mm/min(N/10 mm) After 30 min (Thickness of PSA sheet: 40 μm)

As shown in the table, it was confirmed that according to the PSA sheetsof Examples C1 to C8 in each of which at least either its syrup oroligomer comprised a monomer A as its monomeric component, the to-EPDMpeel strength was greater as compared to the PSA sheet of Example C9 inwhich neither included a monomer A in the monomeric components. ExampleC4 with m_(A)/m_(T) above 2.6% produced yet greater to-EPDM peelstrength as compared to Example C3 with m_(A)/m_(T) at or below 2.6%.

According to Examples C3, C4, C5, C7 and C8 in each of which both thesyrup and oligomer comprised the monomer A as their monomericcomponents, the to-EPDM peel strength was higher as compared to ExampleC2 using an oligomer whose monomeric components were free of a monomer Aor Examples C1 and C6 using no oligomers. In particular, with respect toExamples C4, C5, C7 and C8 with A_(O)/A_(S) at or above 0.5, yet greaterto-EPDM peel strength was obtained as compared to Example C3 withA_(O)/A_(S) below 0.5. With respect to PSA compositions using the samesyrup, according to Examples C4 and C5 with m_(A)/m_(C) above 0.20,higher to-EPDM peel strength was obtained as compared with Example C3with m_(A)/m_(C) at or below 0.20. Similarly, with respect to PSAcompositions using the same syrup, according to Examples C7 and C8 witha m_(A)/m_(C) value above 0.20, higher to-EPDM peel strength wasobtained as compared with Example C6 with a m_(A)/m_(C) value at orbelow 0.20.

Experiment 7 Preparation of PSA Sheets Example D1

A monomer mixture consisting of 38.2 parts of 2EHA, 38.2 parts of BA,21.2 parts of CHA and 2.3 parts of DMAEM was subjected to partialphotopolymerization in the same manner as Example A1 to obtain syrup(d1) comprising a polymer having a Mw of 70×10⁴ and unreacted monomers.The monomer conversion was about 30%.

To 100 parts of the syrup (d1), were added and mixed 20 parts of theoligomer (c4) prepared in Example C4, 0.10 part of TMPTA and 0.30 partof a photopolymerization initiator (trade name “P-02”) available fromSoken Chemical & Engineering Co., Ltd., to prepare a PSA compositionaccording to this example. Using this PSA composition, but otherwise inthe same manner as Example A1, a PSA sheet according to this example wasobtained.

Examples D2, D3

The amounts of TMPTA to 100 parts of the syrup (d1) were modified to0.12 part and 0.14 part, but otherwise in the same manner as Example D1,PSA sheets according to Examples D2 and D3 were obtained, respectively.

Examples D4, D5

In place of TMPTA, to 100 parts of the syrup (d1), 0.16 part and 0.18part of ethylene oxide-modified trimethylolpropane tri(meth)acrylate(available from Osaka Organic Chemical Industry, Ltd., trade name“VISCOAT 360”) (TMP-3P) were added, respectively. Otherwise in the samemanner as Example D1, PSA sheets according to Examples D4 and D5 wereobtained.

Examples D6 to D10

Using the oligomer (c5) prepared in Example C5 in place of the oligomer(c4), but otherwise in the same manner as Examples D1 to D5, PSA sheetsaccording to Examples D6 to D10 were obtained, respectively.

Examples E1 to E10

A monomer mixture consisting of 37.9 parts of 2EHA, 37.9 parts of BA,21.1 parts of CHA and 3.1 parts of DMAEM was subjected to partialphotopolymerization in the same manner as Example A1 to obtain syrup(e1) comprising a polymer having a weight average molecular weight (Mw)of 70×10⁴ and unreacted monomers. The monomer conversion was about 30%.

Using the syrup (e1) in place of the syrup (d1), but otherwise in thesame manner as Examples D1 to D10, PSA sheets according to Examples E1to E10 were obtained, respectively.

The Tg of the syrup (e1) used in Examples E1 to E10 is about −48° C.,the Tg of the oligomer (c4) used in Examples E1 to E5 is about 50° C.,and the Tg of the oligomer (c5) used in Examples E6 to E10 is about 40°C. The Tg values determined from the compositions of the entiremonomeric components constituting the PSA layers of the PSA sheetsaccording to Examples E1 to E10 are around −36° C. to −38° C.

Example E11

A monomer mixture consisting of 40 parts of 2EHA, 40 parts of BA and 20parts of CHA was subjected to partial photopolymerization in the samemanner as Example C1 to obtain syrup (e11) comprising a polymer having aweight average molecular weight (Mw) of 70×10⁴ and unreacted monomers.The monomer conversion was about 30%.

To 100 parts of the syrup (e11), were added and mixed 20 parts of theoligomer (b8) prepared in Example B8, 0.12 part of TMPTA and 0.30 partof a photopolymerization initiator (trade name “P-02”) available fromSoken Chemical & Engineering Co., Ltd., to prepare a PSA compositionaccording to this example. Using this PSA composition, but otherwise inthe same manner as Example A1, a PSA sheet according to this example wasobtained.

Examples F1 to F10

A monomer mixture consisting of 37.6 parts of 2EHA, 37.6 parts of BA,20.9 parts of CHA and 3.8 parts of DMAEM was subjected to partialphotopolymerization in the same manner as Example A1 to obtain syrup(f1) comprising a polymer having a weight average molecular weight (Mw)of 70×10⁴ and unreacted monomers. The monomer conversion was about 30%.

Using the syrup (f1) in place of the syrup (d1), but otherwise in thesame manner as Examples D1 to D10, PSA sheets according to Examples F1to F10 were obtained, respectively.

[Evaluation of Properties]

(To-EPDM Peel Strength at Tensile Speed 300 mm/min)

Using a standard EPDM piece described earlier as the adherend, 180°adhesive strength (to-EPDM peel strength) was measured by the followingprocedure. In particular, each PSA sheet obtained above was cut into a15 mm wide strip to fabricate a measurement sample. The PET film(release liner) covering its first adhesive face was removed and 25 μmthick PET film with no release treatment was applied to back the PSAsheet. In a standard environment at 23° C. and 50% RH, the release linercovering the second adhesive face of the sample was removed and the PSAsheet was press-bonded to the adherend with a 2 kg roller moved back andforth once. This was stored in the standard environment for a prescribedtime period. Subsequently, in the same environment, 180° peel strength(N/15 mm) was measured at a tensile speed of 300 mm/min, using auniversal tensile and compression testing machine (available fromMinebea Co., Ltd., system name “Tensile/Compression Tester, TG-1kN”),based on JIS Z0237(2004).

In the peel strength measurement, the PSA sheet was press-bonded afterthe adherend surface was cleaned by wiping twice in one direction withIPA-wet cloth. The peel strength was measured after 20 minutes and after7 days from the press-bonding.

(Holding Power)

Each PSA sheet obtained above was cut into a 20 mm wide strip tofabricate a measurement sample. The PET film (release liner) coveringits first adhesive face was removed and 25 μm thick PET film with norelease treatment was applied to back the PSA sheet. Subsequently, therelease liner covering the second adhesive face of the sample wasremoved and the sample was applied at its one end to a stainless steel(SUS) plate as the adherend over a 20 mm wide by 20 mm long bondingarea. This was stored in a standard environment at 23° C. and 50% RH for30 minutes. Based on JIS Z0237(2004), the SUS plate was then verticallysuspended in an environment at 40° C. and a 500 g load was applied tothe free end of the sample. After stored with the load applied theretofor two hours in the environment at 40° C., the time taken for thesample to peel from the SUS plate and fall off was measured. Withrespect to a sample that did not fall after two hours, the distance (mm)moved from the initially-adhered location was measured. Two measurements(i.e. n=2) were taken and the average time to fall or the averagedistance moved after two hours wad determined. When one sample fell, butthe other did not, both results were noted.

The results are shown in Table 8 to Table 10. These tables also show thegel fractions measured by the aforementioned method with respect to thePSA layers constituting the PSA sheets according to the respectiveexamples.

TABLE 8 Ex. D1 D2 D3 D4 D5 D6 D7 D8 D9 D10 Syrup composition (parts)2EHA 38.2 38.2 38.2 38.2 38.2 38.2 38.2 38.2 38.2 38.2 BA 38.2 38.2 38.238.2 38.2 38.2 38.2 38.2 38.2 38.2 CHA 21.2 21.2 21.2 21.2 21.2 21.221.2 21.2 21.2 21.2 DMAEM 2.3 2.3 2.3 2.3 2.3 2.3 2.3 2.3 2.3 2.3 Total99.9 99.9 99.9 99.9 99.9 99.9 99.9 99.9 99.9 99.9 Oligomer compositionCHMA 70 70 70 70 70 50 50 50 50 50 (parts) DMAEM 30 30 30 30 30 50 50 5050 50 Total 100 100 100 100 100 100 100 100 100 100 Oligomer Mw (×10⁴)0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 PSA Syrup 100 100 100 100 100100 100 100 100 100 composition Oligomer 20 20 20 20 20 20 20 20 20 20(parts) Crosslinking TMPTA 0.10 0.12 0.14 — — 0.10 0.12 0.14 — — agentTMP-3P — — — 0.16 0.18 — — — 0.16 0.18 Initiator P-02 0.30 0.30 0.300.30 0.30 0.30 0.30 0.30 0.30 0.30 m_(A)/m_(T) (%) 6.9 6.9 6.9 6.9 6.910.3 10.3 10.3 10.3 10.3 A_(O)/A_(S) 2.6 2.6 2.6 2.6 2.6 4.3 4.3 4.3 4.34.3 m_(C)/m_(T) (%) 29.4 29.4 29.4 29.4 29.4 26.0 26.0 26.0 26.0 26.0m_(A)/m_(C) 0.24 0.24 0.24 0.24 0.24 0.39 0.39 0.39 0.39 0.39 Gelfraction (%) 25.5 33.9 36.9 30.8 30.3 0.3 6.5 32.4 1.5 24.8 to-EPDM Peelstrength After 20 min 2.8 2.4 2.6 2.9 2.9 3.1 2.6 2.7 2.6 2.6 300 mm/min(N/15 mm) After 7 days 3.3 2.9 3.1 3.2 3.2 3.5 3.0 2.8 3.2 3.2 Holdingpower 40° C., 34 min 1.7 mm 0.8 mm 5.1 mm 2.1 mm 5 min 41 min 3.3 mm 18min 47 min 500 g, 2 hr (Thickness of PSA sheet: 40 μm)

TABLE 9 Ex. E1 E2 E3 E4 E5 E6 E7 E8 E9 E10 E11 Syrup composition (parts)2EHA 37.9 37.9 37.9 37.9 37.9 37.9 37.9 37.9 37.9 37.9 40 BA 37.9 37.937.9 37.9 37.9 37.9 37.9 37.9 37.9 37.9 40 CHA 21.1 21.1 21.1 21.1 21.121.1 21.1 21.1 21.1 21.1 20 DMAEM 3.1 3.1 3.1 3.1 3.1 3.1 3.1 3.1 3.13.1 — Total 100 100 100 100 100 100 100 100 100 100 100 Oligomer CHMA 7070 70 70 70 50 50 50 50 50 100 composition DMAEM 30 30 30 30 30 50 50 5050 50 — (parts) Total 100 100 100 100 100 100 100 100 100 100 100Oligomer Mw (×10⁴) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 PSA Syrup100 100 100 100 100 100 100 100 100 100 100 composition Oligomer 20 2020 20 20 20 20 20 20 20 20 (parts) Crosslinking TMPTA 0.10 0.12 0.14 — —0.10 0.12 0.14 — — 0.12 agent TMP-3P — — — 0.16 0.18 — — — 0.16 0.18 —Initiator P-02 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30m_(A)/m_(T) (%) 7.6 7.6 7.6 7.6 7.6 10.9 10.9 10.9 10.9 10.9 —A_(O)/A_(S) 1.9 1.9 1.9 1.9 1.9 3.2 3.2 3.2 3.2 3.2 — m_(C)/m_(T) (%)29.3 29.3 29.3 29.3 29.3 25.9 25.9 25.9 25.9 25.9 33.3 m_(A)/m_(C) 0.260.26 0.26 0.26 0.26 0.42 0.42 0.42 0.42 0.42 — Gel fraction (%) 33 32.142.6 33.1 34.5 0.4 12.3 33.2 0.4 31.2 35.2 to-EPDM Peel strength After20 min 3.4 3.1 2.9 3.1 3.5 4.0 3.2 3.2 3.4 3.7 1.2 300 mm/min (N/15 mm)After 7 days 4.8 4.7 4.0 4.4 4.5 5.1 4.6 4.6 5.7 5.9 1.5 Holding power40° C., 8.4 mm 3.0 mm 0.7 mm 10.4 mm 1.2 mm 7 min 36 min 1.9 mm 6 min 40min 1.2 mm 500 g, 2 hr  42 min   50 min (Thickness of PSA sheet: 40 μm)

TABLE 10 Ex. F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 Syrup composition (parts)2EHA 37.6 37.6 37.6 37.6 37.6 37.6 37.6 37.6 37.6 37.6 BA 37.6 37.6 37.637.6 37.6 37.6 37.6 37.6 37.6 37.6 CHA 20.9 20.9 20.9 20.9 20.9 20.920.9 20.9 20.9 20.9 DMAEM 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8 Total99.9 99.9 99.9 99.9 99.9 99.9 99.9 99.9 99.9 99.9 Oligomer (parts) CHMA70 70 70 70 70 50 50 50 50 50 composition DMAEM 30 30 30 30 30 50 50 5050 50 Total 100 100 100 100 100 100 100 100 100 100 PSA compositionSyrup 100 100 100 100 100 100 100 100 100 100 (parts) Oligomer 20 20 2020 20 20 20 20 20 20 Crosslinking TMPTA 0.10 0.12 0.14 — — 0.10 0.120.14 — — agent TMP-3P — — — 0.16 0.18 — — — 0.16 0.18 Initiator P-020.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 m_(A)/m_(T) (%) 8.28.2 8.2 8.2 8.2 11.5 11.5 11.5 11.5 11.5 A_(O)/A_(S) 1.6 1.6 1.6 1.6 1.62.6 2.6 2.6 2.6 2.6 m_(C)/m_(T) (%) 29.1 29.1 29.1 29.1 29.1 25.8 25.825.8 25.8 25.8 m_(A)/m_(C) 0.28 0.28 0.28 0.28 0.28 0.45 0.45 0.45 0.450.45 Gel fraction (%) 28.1 33 41.9 29.4 36.7 0.4 12.2 34.4 1.6 30to-EPDM Peel strength After 20 min 2.4 2.4 2.8 3.4 2.6 2.8 3.0 2.6 3.02.9 300 mm/min [N/15 mm] After 7 days 3.7 3.9 4.4 5.0 3.5 3.7 3.9 3.64.4 4.2 Holding power 40° C., 500 g, 2 hr 5.5 mm 1.2 mm 0.6 mm 3.9 mm0.8 mm 10 min 46 min 1.3 mm 26 min 4.1 mm (Thickness of PSA sheet: 40μm)

As shown in Table 8 to Table 10, with respect to the PSA sheet ofExamples D1 to D10, E1 to E10 and F1 to F10 each comprising a monomer Aas a monomeric component of the acrylic polymer in the adhesive layer,clearly high to-EPDM peel strength was produced both initially (after 20minutes) and after aged (after 7 days) as compared with the PSA sheet ofExample E11 not including a monomer A in its monomeric components. Fromthe results shown in these table, in view of the cohesion (holdingpower) of the PSA, it can be seen that the gel fraction is preferably25% or higher, or more preferably 30% or higher.

Experiment 8 Preparation of PSA Sheets Example G1

A monomer mixture consisting of 79 parts of 2EHA, 20.3 parts of CHA and0.8 part of DMAEM was subjected to partial photopolymerization in thesame manner as Example A1 to obtain syrup (g1) comprising a polymerhaving a weight average molecular weight (Mw) of 30×10⁴ and unreactedmonomers. The monomer conversion was about 30%.

To 100 parts of the syrup (g1), were added and mixed 20 parts of theoligomer (c4) prepared in Example C4, 0.10 part of TMPTA and 0.30 partof a photopolymerization initiator (trade name “P-02”) available fromSoken Chemical & Engineering Co., Ltd., to prepare a PSA compositionaccording to this example. Using this PSA composition, but otherwise inthe same manner as Example A1, a PSA sheet according to this example wasobtained.

Example G2

Using a monomer mixture consisting of 50 parts of CHMA, 20 parts ofisobornyl methacrylate (IBXMA) and 30 parts of DEAEM, but otherwise inthe same manner as the preparation of the acrylic oligomer (b1), anacrylic oligomer (g2) was obtained, having a Mw of 0.5×10⁴. Using theoligomer (g2) in place of the oligomer (c4), but otherwise in the samemanner as Example G1, a PSA sheet according to this example wasobtained.

Example G3

Using a monomer mixture consisting of 15 parts of CHMA, 35 parts ofIBXMA and 50 parts of DEAEM, but otherwise in the same manner as thepreparation of the acrylic oligomer (b1), an acrylic oligomer (g3) wasobtained, having a Mw of 0.5×10⁴. Using the oligomer (g3) in place ofthe oligomer (c4), but otherwise in the same manner as Example G1, a PSAsheet according to this example was obtained.

Example G4

Using the oligomer (c5) prepared in Example C5 in place of the oligomer(c4) prepared in Example C4, but otherwise in the same manner as ExampleG1, a PSA sheet according to this example was obtained.

[Evaluation of Properties]

(To-EPDM Peel Strength at Tensile Speed 300 mm/min)

The respective PSA sheets obtained above were measured for to-EPDM peelstrength in the same manner as in Experiment 4.

The peel strength was measured after 20 minutes and after 7 days fromthe press-bonding of the PSA sheets for the following two cases: (1) thePSA sheet was press-bonded to the adherend surface as it was (i.e.without the cleaning treatment) and (2) the PSA sheet was press-bondedafter the adherend surface was wiped twice in one direction with IPA-wetcloth.

The results are shown in Table 11.

TABLE 11 Ex. G1 G2 G3 G4 Syrup composition (parts) 2EHA 79 79 79 79 CHA20.3 20.3 20.3 20.3 DMAEM 0.8 0.8 0.8 0.8 Total 100.1 100.1 100.1 100.1Oligomer (parts) CHMA 70 50 15 50 composition IBXMA — 20 35 — DMAEM 3030 50 50 Total 100 100 100 100 Oligomer Mw (×10⁴) 0.5 0.5 0.5 0.5 PSAcomposition Syrup 100 100 100 100 (parts) Oligomer 20 20 20 20Crosslinking TMPTA 0.10 0.10 0.10 0.10 agent Initiator P-02 0.30 0.300.30 0.30 m_(A)/m_(T) (%) 5.7 5.7 9.0 9.0 A_(O)/A_(S) 7.5 7.5 12.5 12.5m_(C)/m_(T) (%) 28.6 28.6 25.2 25.2 m_(A)/m_(C) 0.20 0.20 0.36 0.36to-EPDM Not cleaned After 20 min 3.2 2.8 4.4 2.0 Peel strength After 7days 3.2 3.0 3.6 2.3 300 mm/min Cleaned After 20 min 4.5 3.7 5.1 2.3(N/15 mm) After 7 days 3.0 3.2 15.5# 2.8 (Thickness of PSA sheet: 40 μm)*The symbol “#” following a peel strength value indicates cohesivefailure.

As shown in the table, the PSA sheets of Examples G2 and G3 each using acopolymer of CHMA, IBXMA and a monomer A showed great adhesion to EPDM,comparable to the PSA sheets of Examples G1 and G4 each using acopolymer of CHMA and a monomer A as the oligomer. In particular, theresults of Example G3 suggests that the use of an oligomer having acopolymer composition comprising IBXMA and a monomer A can bring about aPSA sheet that exhibits particularly excellent to-EPDM peel strength.

Experiment 9 Preparation of PSA Sheets Examples J1 to J4

PSA compositions according to Examples E2, E5, E7 and E10 were used andthe PSA compositions were applied each to a thickness of 50 μm afterlight irradiation, but otherwise in the same manner as Example D1, PSAsheets according to Examples J1, J2, J3 and J4 were obtained.

Example J5

To 100 parts of the syrup (e11) prepared in Example E11, were added andmixed 20 parts of the oligomer (c4) prepared in Example C4, 0.12 part ofTMPTA and 0.30 part of a photopolymerization initiator (trade name“P-02”) available from Soken Chemical & Engineering Co., Ltd., toprepare a PSA composition according to this example. Using this PSAcomposition, but otherwise in the same manner as Example J1, a PSA sheetaccording to this example was obtained.

Example J6

The PSA composition according to Example E11 was used and the PSAcomposition was applied to a thickness of 50 μm after light irradiation,but otherwise in the same manner as Example D1, a PSA sheet according tothis example was obtained.

The PSA sheets obtained above were measured for peel strength to variousadherends.

(To-EPDM Peel Strength)

Using a standard EPDM piece described earlier as the adherend, 180°adhesive strength (to-EPDM peel strength) was measured by the followingprocedure. In particular, each PSA sheet obtained above was cut into a10 mm wide strip to fabricate a measurement sample. The PET film(release liner) covering its first adhesive face was removed and 25 μmthick PET film with no release treatment was applied to back the PSAsheet. In a standard environment at 23° C. and 50% RH, the release linercovering the second adhesive face of the sample was removed and the PSAsheet was press-bonded to the adherend with a 2 kg roller moved back andforth once. This was stored in the standard environment for a prescribedtime period. Subsequently, in the same environment, 180° peel strength(N/10 mm) was measured at a tensile speed of 300 mm/min, using auniversal tensile and compression testing machine (available fromMinebea Co., Ltd., system name “Tensile/Compression Tester, TG-1kN”),based on JIS Z0237(2004).

In the peel strength measurement, the PSA sheet was press-bonded afterthe adherend surface was cleaned by wiping twice in one direction withIPA-wet cloth. The peel strength was measured after 7 days from thepress-bonding.

(To-PP Peel Strength)

As the adherend, a polypropylene plate (PP plate) available fromShin-Kobe Electric Machinery Co., Ltd., was used. In the cleaningtreatment before press-bonding, ethanol was used in place of IPA and thewiping with the ethanol was performed twice in one direction. Otherwisein the same manner as the to-EPDM peel strength measurement, the otheradhesive face of the measurement sample was press-bonded to theadherend. After 20 minutes and after 7 days from the press-bonding, 180°peel strength (N/10 mm) was measured at a tensile speed of 300 mm/min inthe same manner as the to-EPDM peel strength measurement.

(To-ABS Peel Strength)

As the adherend, an acrylonitrile-butadiene-styrene copolymer resinplate (ABS plate) available from Shin-Kobe Electric Machinery Co., Ltd.,was used, but otherwise in the same manner as the to-PP peel strengthmeasurement, 180° peel strength (N/10 mm) after 20 minutes and after 7days from the press-bonding was measured.

(To-PS Peel Strength)

As the adherend, a high-density polystyrene plate (PS plate) availablefrom PR Topla, Ltd., was used, but otherwise in the same manner as theto-PP peel strength measurement, 180° peel strength (N/10 mm) after 20minutes and after 7 days from the press-bonding was measured.

The results are shown in Table 12.

TABLE 12 J1 J2 J3 J4 J5 J6 Syrup composition (parts) 2EHA 37.9 37.9 37.937.9 40 40 BA 37.9 37.9 37.9 37.9 40 40 CHA 21.1 21.1 21.1 21.1 20 20DMAEM 3.1 3.1 3.1 3.1 — — Total 100 100 100 100 100 100 Oligomer (parts)CHMA 70 70 50 50 70 100 composition DMAEM 30 30 50 50 30 — Total 100 100100 100 100 100 Oligomer Mw (×10⁴) 0.5 0.5 0.5 0.5 0.5 0.5 PSAcomposition Syrup 100 100 100 100 100 100 (parts) Oligomer 20 20 20 2020 20 Crosslinking TMPTA 0.12 — 0.12 — 0.12 0.12 agent TMP-3P — 0.18 —0.18 — — Initiator P-02 0.30 0.30 0.30 0.30 0.30 0.30 m_(A)/m_(T) (%)7.6 7.6 10.9 10.9 5.0 — A_(O)/A_(S) 1.9 1.9 3.2 3.2 — — m_(C)/m_(T) (%)29.3 29.3 25.9 25.9 28.3 33.3 m_(A)/m_(C) 0.26 0.26 0.42 0.42 0.18 —Peel strength to-EPDM After 7 days 3.8 2.6 10.4 13.8# 2.5 1.5 300 mm/minto-PP After 20 min 5.3 4.0 3.9 3.4 3.8 2.1 (N/10 mm) After 7 days 5.84.8 4.1 3.6 4.4 3.3 to-ABS After 20 min 4.9 4.6 5.4 5.0 4.5 3.8 After 7days 6.8 6.0 8.6 7.0 5.2 4.5 to-PS After 20 min 6.3 5.5 5.9 5.3 5.1 3.2After 7 days 9.4 8.4 8.7 8.1 7.5 4.8 (Thickness of PSA sheet: 50 μm)*The symbol “#” following a peel strength value indicates cohesivefailure.

As shown in the table, the PSA sheets of Examples J1 to J5 obtained fromPSA compositions comprising a monomer A in their monomeric componentswere clearly superior in to-EPDM peel strength as compared to the PSAsheet of Example J6 obtained from a PSA composition comprising nomonomer A in its monomeric components. These PSA sheets of Examples J1to J5 also showed great adhesion to a polyolefin (polypropylene herein)being a low-polar material. It also exhibited high peel strengthrelative to the ABS plate and polystyrene plate. As described here, thePSA sheets of Examples J1 to J5 exhibited excellent adhesion to varioustypes of adherend due to their improved adhesion to low-polar surfaces.Among Examples J1 to J4 obtained from PSA compositions in each of whichboth the syrup and oligomer included the monomer A in their monomericcomponents, there was a tendency to produce even greater results ascompared to Example J5 obtained from a PSA composition in which just oneof the syrup and oligomer comprised the monomer A in its monomericcomponents.

Experiment 10 Preparation of PSA Sheets Comprising Bubble-ContainingLayers Example M1

The PSA composition was applied to a thickness of 90 μm after lightirradiation, but otherwise in the same manner as Example E2, a PSA sheetconsisting of a bubble-free layer was prepared. The PSA sheet wasadhered to one surface of the 12 mm thick bubble-containing adhesivelayer prepared in Example L1. A PSA sheet having a total thickness ofabout 1.29 mm was thus obtained, having a bubble-containing adhesivelayer and a bubble-free adhesive layer (PSA layer (A)) overlaid on oneface thereof. The PSA sheet according to Example M1 was subjected to thefollowing evaluation of properties.

[Evaluation of Properties]

Each PSA sheet was cut into a 10 mm wide strip to prepare a measurementsample. The PET film (release liner) covering its first adhesive face(the surface of the bubble-containing adhesive layer) was removed and 50μm thick PET film with no release treatment was applied to back the PSAsheet. In a standard environment at 23° C. and 50% RH, the release linercovering the second adhesive face (the surface of the bubble-freeadhesive layer) of the measurement sample was removed and the PSA sheetwas press-bonded to the adherend with a 2 kg roller moved back and forththree times.

As the adherend, a standard EPDM piece was used. The back face of theadherend was lightly wiped with IPA-wet cloth and the back face wasfixed via double-coated tape to a PP plate to fabricate an adherendunit. The adherend unit was stored in an environment at a prescribedtemperature to condition the adherend to the prescribed temperature(adherend temperature); and the measurement sample was press-bondedimmediately after the adherend unit was removed and placed in thestandard environment without cleaning the adherend surface (surfacesubject to adhesion). The adherend temperature was 0° C., 23° C., 60°C., 80° C., 120° C. or 150° C. The storage time was about two minutes.

The measurement sample press-bonded to the adherend was stored in thestandard environment for 72 hours. Subsequently, in the sameenvironment, 180° peel strength (N/10 mm) was measured at a tensilespeed of 50 mm/min, using a universal tensile and compression testingmachine (available from Minebea Co., Ltd., system name“Tensile/Compression Tester, TG-1kN”), based on JIS Z0237(2004). Theresults are shown in Table 13.

TABLE 13 To-EPDM peel strength Press-bonding Adherend Measurement at 50mm/min Temperature Temperature Temperature (N/10 mm) 23° C.  0° C. 23°C. 5.7 23° C. 23° C. 23° C. 5.6 23° C. 60° C. 23° C. 6.0 23° C. 80° C.23° C. 9.4 23° C. 120° C.  23° C. 9.9 23° C. 150° C.  23° C. 10.1

As shown in the table, it was found that when the PSA sheet was appliedto the adherend heated to a temperature above ordinary temperature, thepeel strength tended to further increase. Particularly great resultswere obtained at or above 75° C. of adherend temperature.

Although specific embodiments of the present invention have beendescribed in detail above, these are merely for illustrations and do notlimit the scope of the claims. The art according to the claims includesvarious modifications and changes made to the specific embodimentsillustrated above.

As evident from the description above, matters disclosed by thisdescription include the following.

(1a) A PSA sheet,

with at least one surface thereof being formed as an adhesive face,

the at least one surface being a surface of an acrylic PSA layercomprising an acrylic polymer,

the acrylic polymer comprising an amino group-containing (meth)acrylateas its monomeric component, and

the PSA sheet comprising at least one bubble-containing layer.

(2a) The PSA sheet according to (1a) above, comprising a support layerthat includes the bubble-containing layer and the acrylic PSA layersupported with the support layer.(3a) The PSA sheet according to (1a) or (2a) above, having, as thebubble-containing layer, a bubble-containing adhesive layer formed of aPSA including bubbles.(4a) The PSA sheet according to any of (1a) to (3a) above, having, asthe bubble-containing layer, a foam sheet that comprises a foam bodylayer formed with a plastic foam body.(5a) The PSA sheet according to any of (1a) to (4a), having a 10%compression hardness of 0.01 Pa to 0.07 Pa.(6a) The PSA sheet according to any of (1a) to (5a), having a breakingstrength of 0.3 Pa to 2.5 Pa.

As evident from the description above, matters disclosed by thisdescription further include the following.

(1b) A PSA sheet to be applied to a surface formed of an olefinic rubbermaterial,

the PSA sheet having an adhesive face to be applied to the surfaceformed of the olefinic rubber material,

the adhesive face being a surface of an acrylic PSA layer comprising anacrylic polymer, and

the acrylic polymer comprising an amino group-containing (meth)acrylateas its monomeric component.

(2b) The PSA sheet for application to olefinic rubber according to (1b)above, wherein the amino group-containing (meth)acrylate is included ata ratio higher than 2.6% by mass of monomeric components of all polymersin the acrylic PSA layer.(3b) The PSA sheet for application to olefinic rubber according to (1b)or (2b) above, wherein

the acrylic PSA layer is a layer formed with an acrylic PSA composition,

the acrylic PSA composition comprises a polymerization product (a) of amonomer mixture comprising an acyclic alkyl (meth)acrylate, and

the monomer mixture includes the amino group-containing (meth)acrylateat a ratio higher than 0.2% by mass or the monomer mixture.

(4b) The PSA sheet for application to olefinic rubber according to anyone of (1b) to (3b) above, wherein

the acrylic PSA layer is a layer formed with an acrylic PSA composition,

the acrylic PSA composition comprises a polymerization product (a) of amonomer mixture comprising an acyclic alkyl (meth)acrylate and anacrylic oligomer (b) having a weight average molecular weight of 2×10⁴or less, and

at least either the polymerization product (a) or the acrylic oligomer(b) comprises the amino group-containing (meth)acrylate as its monomericcomponent.

(5b) The PSA sheet for application to olefinic rubber according to (4b)above, wherein each of the polymerization product (a) and the acrylicoligomer (b) comprises the amino group-containing (meth)acrylate as itsmonomeric component.(6b) A PSA sheet-bearing part comprising

a part having a surface formed of an olefinic rubber material, and

a PSA sheet of which at least one surface is formed as an adhesive face,

the adhesive face being adhered to the surface formed of the olefinicrubber material,

the adhesive face being a surface of an acrylic PSA layer comprising anacrylic polymer, and

the acrylic polymer comprising an amino group-containing (meth)acrylateas its monomeric component.

(7b) The PSA sheet-bearing part according to (6b) above, wherein theadhesive face is directly adhered to the surface formed of the olefinicrubber material.(8b) The PSA sheet-bearing part according to (6b) or (7b) above, whereinthe olefinic rubber material comprises an ethylene-propylene-dienerubber as a primary polymer component.(9b) The PSA sheet-bearing part according to any of (6b) to (8b) above,wherein the olefinic rubber material comprises carbon black.(10b) The PSA sheet-bearing part according to any of (6b) to (9b) above,wherein the part having the surface formed of the olefinic rubbermaterial is a weather strip.(11b) A method for producing a PSA sheet-bearing part, the methodcomprising

a step of obtaining a molded olefinic rubber body having a surfaceformed of an olefinic rubber material,

a step of obtaining a PSA sheet in which at least one surface is formedas an adhesive face, and

a step of applying the adhesive face to the surface formed of theolefinic rubber material, wherein

the adhesive face is a surface of an acrylic PSA layer comprising anacrylic polymer, and

the acrylic polymer comprises an amino group-containing (meth)acrylateas its monomeric component.

(12b) The method according to (11b), wherein, in the step of applyingthe adhesive face, the adhesive face is directly applied to the surfaceformed of the olefinic rubber material.(13b) The method according to (11b) or (12b), wherein the surface formedof the olefinic rubber material is subjected to cleaning treatment bywhich a cleaning liquid comprising an organic solvent is allowed to makecontact with the surface and the adhesive face is directly applied tothe cleaned surface.(14b) The method according to any of (11b) to (13b), wherein the step ofapplying the adhesive face is carried out at ordinary temperature.(15b) The method according to any of (11b) to (14b), wherein the moldedolefinic rubber body is a weather strip.

REFERENCE SIGNS LIST

-   1, 2, 3, 5, 10, 20, 30, 40 PSA sheets-   21 first PSA layer (acrylic PSA layer)-   21A first adhesive face-   21B second adhesive face-   22 second PSA layer-   22A second adhesive face-   23 intermediate layer-   31 backside layer-   50, 500 PSA sheet-bearing parts-   52 door weather strip (part)-   52A surface (surface subject to adhesion)-   60 door panel-   60A surface-   121 bubble-containing adhesive layer (bubble-containing layer)-   121A first adhesive face-   121B second adhesive face-   221 first PSA layer (bubble-free layer)-   221A first adhesive face-   222 second PSA layer (bubble-free layer)-   222A second adhesive face-   223 intermediate layer (bubble-containing layer, support layer)-   321 first PSA layer (bubble-free layer)-   321A first adhesive face-   322 second PSA layer (bubble-containing layer, support layer)-   322A second adhesive face-   421 PSA layer (bubble-free layer)-   421A adhesive face-   431 backside layer (bubble-containing layer, support layer)

1. A pressure-sensitive adhesive sheet having an adhesive face, theadhesive face being formed of an acrylic pressure-sensitive adhesivelayer comprising an acrylic polymer, and the pressure-sensitive adhesivesheet having a peel strength of 5 N/10 mm or greater, the peel strengthis measured as such that the adhesive face is directly adhered to anethylene-propylene-diene rubber surface and after 20 minutes, peeled inthe 180° direction at a tensile speed of 50 mm/min.
 2. Thepressure-sensitive adhesive sheet according to claim 1, comprising asupport layer comprising a bubble-containing layer and the acrylicpressure-sensitive adhesive layer supported with the support layer. 3.The pressure-sensitive adhesive sheet according to claim 1, having a 10%compression hardness of 0.01 Pa to 0.07 Pa.
 4. The pressure-sensitiveadhesive sheet according to claim 1, having a breaking strength of 0.3Pa to 2.5 Pa.
 5. The pressure-sensitive adhesive sheet according toclaim 1, having an overall thickness of 0.05 mm to 10 mm.
 6. Thepressure-sensitive adhesive sheet according to claim 1, wherein theacrylic polymer comprises an amino group-containing (meth)acrylate asits monomeric component.
 7. The pressure-sensitive adhesive sheetaccording to claim 6, wherein the amino group-containing (meth)acrylateis included at a ratio higher than 2.6% by mass of monomeric componentsof all polymers in the acrylic pressure-sensitive adhesive layer.
 8. Thepressure-sensitive adhesive sheet according to claim 6, wherein theacrylic pressure-sensitive adhesive layer is a layer formed with anacrylic pressure-sensitive adhesive composition, the acrylicpressure-sensitive adhesive composition comprises a polymerizationproduct (a) of a monomer mixture comprising an acyclic alkyl(meth)acrylate, and the monomer mixture includes the aminogroup-containing (meth)acrylate at a ratio higher than 0.2% by mass ofthe monomer mixture.
 9. The pressure-sensitive adhesive sheet accordingto claim 6, wherein the acrylic pressure-sensitive adhesive layer is alayer formed with an acrylic pressure-sensitive adhesive composition,the acrylic pressure-sensitive adhesive composition comprises apolymerization product (a) of a monomer mixture comprising an acyclicalkyl (meth)acrylate and an acrylic oligomer (b) having a weight averagemolecular weight of 2×10⁴ or less, and at least either thepolymerization product (a) or the acrylic oligomer (b) comprises theamino group-containing (meth)acrylate as its monomeric component. 10.The pressure-sensitive adhesive sheet according to claim 9, wherein eachof the polymerization product (a) and the acrylic oligomer (b) comprisesthe amino group-containing (meth)acrylate as its monomeric component.11. A pressure-sensitive adhesive sheet-bearing part comprising a parthaving a surface formed of an olefinic rubber material, and apressure-sensitive adhesive sheet of which at least one surface isformed as an adhesive face, wherein the adhesive face is a surface of anacrylic pressure-sensitive adhesive layer comprising an acrylic polymer,the adhesive face is directly adhered to the surface formed of theolefinic rubber material, and the pressure-sensitive adhesive sheet hasa peel strength of 7 N/10 mm or greater, the peel strength is measuredas such that the pressure-sensitive adhesive sheet is peeled from thesurface formed of the olefinic rubber material in the 180° direction ata tensile speed of 50 mm/min.
 12. The pressure-sensitive adhesivesheet-bearing part according to claim 11, wherein the olefinic rubbermaterial comprises an ethylene-propylene-diene rubber as its primarypolymer component.
 13. The pressure-sensitive adhesive sheet-bearingpart according to claim 11, comprising a support layer comprising abubble-containing layer and the acrylic pressure-sensitive adhesivelayer supported with the support layer.
 14. The pressure-sensitiveadhesive sheet-bearing part according to claim 11, with thepressure-sensitive adhesive sheet having a 10% compression hardness of0.01 Pa to 0.07 Pa.
 15. The pressure-sensitive adhesive sheet-bearingpart according to claim 11, with the pressure-sensitive adhesive sheethaving a breaking strength of 0.3 Pa to 2.5 Pa.
 16. Thepressure-sensitive adhesive sheet-bearing part according to claim 11,with the pressure-sensitive adhesive sheet having an overall thicknessof 0.05 mm to 10 mm.
 17. The pressure-sensitive adhesive sheet-bearingpart according to claim 11, wherein the part is a weather strip.
 18. Thepressure-sensitive adhesive sheet-bearing part according to claim 11,wherein the acrylic polymer comprises an amino group-containing(meth)acrylate as its monomeric component.